National Air Filtration Association

Belt Drives

nafa@nafahq.org — Fri, 13 Jun 2025 16:50:27 +0000

Installation, Tensioning & Maintenance of V-Belts

Introduction to Power Transmission Belting used in the HVAC-R Industry

Types of Power Transmission

There are various types of power transmission devices commonly used in industry today. Among them for example, chains, gears, v-belts and synchronous belts are widely used. The focus of this exercise will be a general introduction to rubber power transmission belts and more specifically, those v-belts and synchronous belts used in the Heating, Ventilation, Air Conditioning and Refrigeration (HVAC-R) industry.

Power Transmission Belting

The primary function of a belt is to simply transfer rotation from the powered driver pulley to one or more driven pulleys. The belt must be designed and capable of transferring this torque efficiently and reliably. Generally, the most economical component in the system, belts can also act as a “safety fuse” by slipping or breaking under a peak or shock load situation, such as when a drive becomes jammed by debris, which can protect the more expensive components of the system.

Advantages of Power Transmission Belts

Lowest cost means of transmitting power
Ability to accommodate a wide range of speeds and center distance between driver and driven shaft
Quiet and clean operation
Require no lubrication like chains, gears and gearboxes
Able to absorb shock loads and pulsations
Can be used for special applications such as clutching and variable speed

Two Major Types of Power Transmission Belts

There are two major types of Power Transmission Belts. These are V-Belt and Synchronous Belt (also commonly referred to as timing belt).

Terminology

The terms “sheave” for v-belt drives and “sprocket” for synchronous drives and “pulley” (for all drives) are commonly used when referring to the “wheels” used connect the belt between the driver and driven units of different types of belt drives. The International Standards Organization (ISO) uses the term pulleys for all drives whether they are v-belt or synchronous.

V-Belt

The V-Belt is a friction device and works on the principle of the wedge. It relies on tension to create friction on the sidewall of the sheave to transmit power. It is non-synchronous and allows slippage. Slippage can be desirable and intended in drive design. For example, in a fan where the belt must slip rather than break the belt or bend a shaft if the blade contacts something or is blocked. V-Belts are the most basic belt utilized for power transmission and are generally speaking, also the most economical.

V-Belt Characteristics

Less expensive than most other forms of power transmission
Start, stop and run smoothly
Operate noiselessly and without lubrication
Absorb objectionable and harmful vibrations
Clean and require minimum maintenance
Rugged and long lasting
Accommodate a wide selection of speed ranges
Cover an extremely wide horsepower range
Easy to install and simple to replace
Relatively unaffected by moisture, abrasive dusts, or extreme variations in temperature

Two types of V-Belt Construction are Commonly used in Industry:

Wrapped V-belt - has a protective fabric cover and will allow some slippage in peak torque situations. Slippage can be advantageous in some drives to avoid damage to belt and other drive components
Raw Edge V-belt - has fabric on the top and bottom but no fabric on the “raw edge” sides. This construction resists slippage with more grip on the sheave sidewalls due to the exposed rubber sidewall that has no fabric as a wrapped v-belt does. It is advantageous in drives where minimum slippage, maximum efficiency and power transmission is required. It will still allow slippage but is more resistant to slippage than a wrapped v-belt.

V-Belt Types and Sizes

V-Belts come in a wide variety of sizes and lengths. They are identified by their various cross sections and length.

The common types used in the HVAC-R industry are listed in the table below.

Synchronous Belt

Synchronous or timing belt is a positive engagement device and relies on the accurate meshing of the belt teeth with the sprocket grooves. It does not allow slippage. There are drives where slippage can cause damage and must be prevented. For example, the valve train of some internal combustion engines. If the drive does not maintain synchronous operation the piston can contact and damage the valves. Converting an HVAC V-belt drive to synchronous belt is a way to gain a significant efficiency increase and resulting energy savings.

Use a Synchronous Belt Drive when:

High mechanical drive efficiency and energy savings are a priority
Synchronous transmission and precision positioning between shafts is required
Low maintenance is a priority
High torque, low RPM requirements
Compact drive layout is necessary
Low noise requirements (compared to chain and gears)
Environmental or contamination concerns (no lubrication required such as with chain)

Detachable Tab Link Type V-Belt

Detachable Tab Link V-Belt is an ideal alternative to conventional rubber v-belts in many applications. Made endless by hand using no tools, an open length of belt can be assembled from tabs (like links in a chain) and wrapped around pulleys in hard-to-fit applications yielding fast belt replacement.

For use in applications where it's difficult to install an endless conventional v-belt, avoiding costly labor-intensive machine disassembly.
Ideal for use on mobile service vehicles where carrying a large inventory of v-belts is not practical. A long roll of detachable tab link type v-belt can be carried on the vehicle and any length of belt can be made versus carrying a large inventory of conventional v-belt sizes. Eliminates the possibility of being “out”” of a needed size.
Can be used either as singles or on multiple v-belt drives. Widely used in HVAC, poultry, agriculture and general industry.
Increased calls per day for mobile service vehicles (reduced labor cost and travel spent searching for the right v-belt)
Less vibration and noise than conventional v-belts

Saving Energy with Efficient Belt Drives

The cost of energy in manufacturing has a major effect on overall cost of a product. In fact, energy cost is currently one of the main drivers in reshoring, the growing movement of bringing manufacturing operations back to the United States from offshore locations. By introducing energy efficient belts drives, you can implement a simple, cost-effective solution to achieve energy savings. Proper installation and maintenance combined with the latest drive belt technology can improve efficiency through reduced energy consumption and enhance drive performance.

Regular Maintenance - Synchronous and V-Belt Drives

Proper Tensioning - One third of electric motors employed in industrial and commercial applications use belt drives. The majority of these drives use wrapped (fabric covered) V-belts, relying on the friction between the belt and sheave groove to transmit power. Relatively inexpensive, wrapped V-belts are designed to allow for limited slippage; intended to slip only in potentially problematic situations, this slippage prevents damage to expensive driven equipment by acting as a safety fuse. The belt can slip or break rather than damaging the more expensive driven unit.

But without frequent periodic maintenance, these belt drives tend to slip excessively during normal operation and result in reduced efficiency and increased operating costs. A correctly installed wrapped V-belt drive can attain 95-98% efficiency soon after installation, rapidly declining to approximately 93% efficiency during the course of normal operation. Without continued periodic tensioning maintenance, efficiency will decrease even further and components will wear more quickly. Belt drive tensioning maintenance is often neglected due to higher maintenance priorities, meaning belt drives receive attention only when a belt finally breaks. This situation can be avoided by periodically adjusting the tension, increasing the lifespan of belts and reducing the frequency of service interruptions.

Proven Energy Saving Solutions

The U.S. Department of Energy recommends replacing V-belts with proven belt drive solutions, including cogged raw edge V-belts and synchronous belts, as best practice for increasing belt drive energy efficiency. Upgrading from a wrapped V-belt to a raw-edge cogged belt yields an average 2% increase in efficiency, a good return for a very low-cost investment. For new drives, using synchronous belts can provide an average 5% efficiency increase compared to V-belts. While increases of 2–5% may seem insignificant, when considering the energy cost savings over multiple

drives and longer running times, the savings soon become substantial. The following overview of the available belt options, as well as the pros and cons of each solution, is a useful guide for evaluating and selecting the best belt for the task.

Good: Standard Wrapped V-Belt - Typical Efficiency = up to 93%

The wrapped V-belt is typically the standard belt utilized in many applications. The excellent mechanical characteristics and high transmission efficiency make this type of belt a popular choice.

PROS

The wrapped V-belt will protect the drive from shock loads where torque spikes are present, by allowing some slippage and act as a safety fuse reducing risk of damage to valuable components.

Any application where some slippage is desirable will be better suited to using a wrapped V-belt.
A wrapped V-belt offers more protection against contamination as the cover offers protection to the rubber body of the belt.

CONS

Among available belt drive options, wrapped V-belts are the least efficient.

This type of V-belt requires frequent tensioning to maintain its initial efficiency. If not properly maintained on a regular basis, it will lose up to 20% efficiency.
There is a sharp reduction in efficiency after installation due to slippage, as the V-belt stretches during operation.
There is a large variation in efficiency between V-belts, on multi-belt drives, tension variation between multiple belts can result in a belt that is not working as hard as the others, therefore impacting overall drive efficiency.

Better: Cogged Raw Edge V-Belt – Typical Efficiency = up to 95%

“Raw Edge” construction differs from wrapped v-belt in that it does not have external fabric on the sides of the belt. This puts rubber in direct contact with the pulley grooves greatly reducing slippage. The cogged raw edge V-belt also has notches cut in the underside for cooler operation and greater flexibility, making it ideally suited for smaller diameter pulleys. More efficient than a wrapped V-belt, it is the best choice where a synchronous drive is not cost-effective but greater efficiency is desired.

PROS

The cogged or notched construction reduces bending resistance in the belt, so it is able to bend around smaller diameter pulleys than a wrapped V-belt. Smaller pulleys require less material to produce, meaning they are generally cheaper than larger versions.
The raw edge sidewall construction (meaning no fabric cover) has a greater coefficient of friction than a wrapped V-belt, making it more slip-resistant and allowing it to transmit more power.
A cogged V-belt runs cooler than a wrapped V-belt, and, as a result, will last longer. The US DoE estimates that this belt type is 2% more efficient than standard V-belts.
This belt runs on the same pulleys as a standard V-belt, so upgrading is a simple process of changing the belt without incurring the cost of new components.
Unlike a synchronous belt, a cogged V-belt provides better vibration damping where excessive vibration is a concern.

CONS

Initial cost of raw edge v-belt is higher although return on investment is rapid.

Best: Synchronous Belt – Typical Efficiency = Up to 98%

Also known as “timing belt”, synchronous belt teeth engage with corresponding pulley teeth. This belt eliminates slippage and provides the highest efficiency. However, it is not a direct replacement for existing v-belt drives as it requires a new drive design that will require all new belts and pulleys.

PROS

The teeth in a synchronous drive create positive engagement with the sprockets for zero belt slippage and maximum efficiency.
A synchronous belt is the best choice for new drive applications, as the initial cost is offset against the increased efficiency and reduced downtime for maintenance that it offers.
This belt maintains its efficiency over its lifespan, unlike a standard V-belt, which loses efficiency over time.
This type of drive runs cooler and with less tension than V-belts, which extends the life of both bearings and belts.
Capable of operating in wet and oily conditions that would hinder a V-belt, a synchronous belt requires only minimal maintenance and re-tensioning.

CONS

Conversion of a v-belt drive to synchronous belt will require both new belts and pulleys, making it a higher initial cost than simply replacing v-belts on a v-belt drive.
Synchronous belt generates more noise than V-belt.
A synchronous drive is less suited for applications where some slippage is desirable.
Alignment and tension is critical as synchronous belt is not as tolerant as a V-belt to misalignment.

Preventative maintenance

The implementation of a preventative maintenance program including proper belt drive installation, tensioning procedures and best practices will increase productivity, reduce downtime and yield the additional benefit of improved workplace safety.

The majority of power transmission drive problems are attributed to improper installation and maintenance. This article is intended to provide guidance in avoiding drive problems, extending drive life and maximizing performance while maintaining a safe working environment.

When compared to the cost of production downtime and the labor costs associated with a belt failure, the cost of a belt is relatively insignificant. Generally speaking, at any given production facility, 80% of the downtime related to power transmission belts can be found on 20% of the drives in the plant. In other words, 80% of the drives are fine. The remaining 20% are “problem drives” requiring frequent attention and replacement. Additionally, it’s not uncommon for a large industrial facility to spend thousands of dollars annually to determine what type of replacement belt is needed for a particular drive. Worn belts are often difficult to identify as their part numbers sometimes become impossible to read after lengthy service.

Safety

Power transmission products are potentially dangerous. Failing to follow recommended application information and procedures for installation, and maintenance of products may result in serious bodily injury or death. Make sure that product selected for any application is recommended for that service. Always follow the recommendations of the original equipment manufacturer. Contact Megadyne for specific information.

Before doing any maintenance work on power drives, always switch off the power and lockout the drive. A tag should be attached stating, "Danger - do not operate."
One should always try to operate the equipment after shutdown to make sure you have locked-out the proper switchbox, ensuring that the switchbox is operating properly and also to release any stored energy.
Use belt guards to provide protection for personnel from contact with drive components. Never test or operate belt drives without guards in place.
Always wear gloves to protect from sharp edges and hot surfaces.
Never wear loose or bulky clothing in close proximity to an unguarded drive where it could become entangled in the drive and cause injury to personnel.
Always be aware of pinch points where hands and fingers can be injured, especially where the belt enters the sheave or sprocket.
Always keep the area around the drive free of clutter and debris.
Never re-use damaged pulleys. They should be replaced if not repairable.
Always use static dissipating belts in conjunction with industry approved methods to dissipate electrical charges on drives used in hazardous atmospheres.
Never use Megadyne belts for aircraft applications. Megadyne belts are not designed for or intended for use on aircraft propellers, rotors or accessory drives. Do not use on helicopters or private, commercial, ultralight or any other airborne aircraft application.

Installation & maintenance

Most drives fail due to improper installation & maintenance.
(see Figure 1)

Good installation & maintenance practices ensure…
Longer belt life
Lower maintenance costs
Longer drive component life
More efficient drive systems
Energy savings
Safe operation
Increased productivity
Reduced downtime

Belt installation

After correct installment and alignment of pulleys you can install the belts. Always move the drive unit, usually an electric motor mounted on an adjustable base, to decrease the drive center distance and create slack so you can easily slip the belts onto the pulleys without force. Never force belts onto a drive with a tool such as a screwdriver or a pry bar. Doing so will rupture the fabric cover or break the load-carrying cords inside the belt.

Proper belt tension

Proper belt tension is essential for maximum belt life and efficiency. Improper belt tension is the leading cause of premature belt failure and increased costs. Under-tensioned belts lead to slippage, overheating, excessive pulley wear, rollover and noise, all of which lead to higher maintenance costs and inefficient power transmission. Also, over-tensioning belts leads to premature wear of bearings, shafts and pulleys. The result is more frequent replacement of drive components and costly downtime. Proper tension is the lowest tension at which the belt won’t slip or jump teeth under peak conditions.

V-Belt belt tensioning

V-belt tensioning can be performed using a tension tester gauge using the procedure in Figure 2. After seating the belts in the sheave groove and adjusting center distance to take up slack in the belts, further increase the tension until only a slight bow on the slack side is apparent while the drive is operating under load. Stop the drive and use the gauge to measure the necessary force to depress the belt and deflect 1/64-inch for every inch of belt span (use center belt on multiple belt drives).

For example, a deflection for a 50-inch belt span is 50/64ths, or 25/32-inch. The amount of force required to deflect the belt should compare with the deflection forces noted in Megadyne technical manuals.

Best practices

Matching V-Belts. When using multiple grooved sheaves, be sure that all of the belts are the same brand. Always replace complete sets of v-belts even if only one is worn or damaged.

Proper alignment is essential for long belt life. Check belt alignment whenever you maintain or replace belts or whenever you remove or install pulleys.

Select Correct V-Belts to match Sheave Grooves
Don’t mix belt brands; stick with one manufacturer
Don’t mix new & used belts
Replace worn pulleys after 3 belt replacements
To check for loose belts, put your fingertips in a sheave groove (after drive shutdown). If sheave is so hot you cannot comfortably keep them there, the belts have probably been slipping.
Ideal tension is the lowest tension where belt will not slip under peak load.
Over-tensioning will shorten belt and bearing life.
Inspect drive periodically. Re-tension the belts if slipping.
If belts slip, check for adequate tension and/or worn sheaves.
Never apply “belt dressings” to belts. These compounds are usually made from a petroleum derivative and can have a destructive effect on rubber compounds and other components of the belt.

Author: Jason Industrial

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Improving Indoor Air Quality During Wildfires

nafa@nafahq.org — Fri, 13 Jun 2025 16:37:04 +0000

Improving Indoor Air Quality During Wildfires

In California and other U.S. western states, wildfires have become more frequent and intense, adversely impacting air quality and human health. Smoke from wildfires contains many toxins and irritants, including particles smaller than 2.5 microns in diameter, which, due to their size, penetrate deep into the lungs and contribute to cardiopulmonary and respiratory illness. Many health agencies and departments suggest people stay indoors during wildfires to limit their exposure to these particles. But how healthy is the air indoors during a wildfire, and can it be improved?

Brett Singer and Rengie Chan¹ are leaders of Berkeley Lab’s Indoor Environment Group. The Indoor Environment Group, which is supported by the Department of Energy, is one of the nation's leading research groups seeking to advance the health, productivity, and energy efficiency of the built environment.

Singer and Chan have worked with California homes, schools, and offices to improve air quality by ensuring adequate ventilation during normal operation and use of high-efficiency filters to reduce particles in indoor air, both during normal air pollution and especially during wildfires. Schools are a particular concern because rates of asthma are higher in children than in adults, and the particles can trigger asthma attacks.

What are the most important factors affecting indoor air quality during wildfires?

Singer: A lot of factors are involved, but the main ones are how the building is ventilated, whether there is any filtration and how effective the filtration system is. During smoke events, most people now know that they should keep windows closed, and that helps. But outdoor air may be coming in through mechanical systems – which occurs in most commercial buildings and some homes – and through uncontrolled air movement through cracks and openings in the building shell. Filtration can be used to remove particles as air is brought into the building by a mechanical system or by recirculating air already inside the building.

By how much do these factors affect the amount of these tiny particles indoors?

Singer: An older home or commercial building that has not been upgraded and doesn’t have high performance filters can have indoor particle levels that are 70% to 80% of outdoor levels even when all the windows are closed. Homes built in the last 10 to 20 years and older homes that have had very good air sealing upgrades can have indoor particle levels that are only 50% or less of those outdoors, when windows are closed. And particle levels can be reduced to less than 20% of outdoor levels with good filtration. Airtight homes or office buildings with high performance filtration can reduce exposures to outdoor particles to less than 5%.

A really good filter has a MERV rating of 12 or better. “MERV” is the minimum efficiency reporting value, one standard way of grading filters. Other common ratings you can find on air filters are MPR (microparticle performance rating) and FPR (filter performance rating); look for MPR of rating 1900 or higher and FPR of rating 9 or higher for good filtration.

What special challenges do schools face during wildfires?

Chan: The occupancy is much higher in a school than in an office environment or home. A typical classroom can have 30 students plus the teacher in roughly 1,000 square feet. We do not advise stopping outdoor air ventilation entirely because it can degrade the indoor air quality and interfere with learning. The solution is to have very good filters installed in the heating, ventilation, and air conditioning (HVAC) system and reduce ventilation to the minimum needed to avoid stuffy conditions. In addition to the exposure to wildfire smoke inside classrooms, schools also face additional concerns of exposing students to high levels of wildfire smoke in the ambient air as they travel from home to school.

What are simple ways to improve indoor air quality during wildfires?

Singer: Keep windows and doors closed. If you are in a house with a mechanical ventilation system, turn it off during the fire. And remember to turn it back on after the fire! If you have access to the building’s HVAC system, install the highest-efficiency air filter that’s compatible with the system. Most systems can handle a MERV 13
filter that has been designed for efficient airflow. And of course, the HVAC system must be operating for the filters to be effective.

Most homes have a “forced air” heating or heating and cooling system and all of these have a filter that can be upgraded for whole-house air cleaning. And modern systems have a “circulation” model that will recirculate house air through the system continuously even if no heating or cooling is needed. This type of operation can be controlled through the thermostat, using a “fan on” or similar setting. If you don’t have access to the HVAC system, get a portable air cleaner designed for the size of the room, or get two if necessary.

If you decide to get a home air monitor, we have tested a number of the more popular low-cost models and have info on our website about how to interpret the numbers.

Chan: Be prepared before wildfires start. Have these higher efficiency air filters on hand and confirm ahead of time that the HVAC system can handle that kind of air filter. Whenever there are extreme events it’s pretty hard to buy filters, but filters make a significant difference. In a study with California schools, we found just replacing MERV 8 filters with MERV 13 filters reduced the amount of these fine particles in school classrooms by 40%. Having indoor air quality monitoring in place before the wildfires start will give you time to know how to read and interpret the information from your air quality monitors.

Are there online resources available?

Singer: Yes! The US EPA has detailed guidance on how to prepare your home and operate it during a smoke event (https://tinyurl.com/EPAWildfireIAQ). And many state air quality and public health agencies provide additional resources, for example (https://tinyurl.com/ProtectFromWildfireSmoke).

What about masks?

Singer: If fitted and worn correctly, respirators can reduce exposure for people who can't avoid being outdoors for extended periods. Guidance is provided in the resources linked above. Using a properly fitted respirator can also carry risks for anyone who already has trouble breathing; so it is important for people to consult with their physicians.

Rengie Chan was a speaker at the 2019 Technical Seminar, presenting on MERV 8 v MERV 13 Analysis with Q&A on PM Monitoring Data During Wildfires.

Author: Jessica Scully reprinted with permission from newswire.com

The post Improving Indoor Air Quality During Wildfires appeared first on National Air Filtration Association.

Clouds of Dust

nafa@nafahq.org — Thu, 29 May 2025 16:23:09 +0000

Clouds of Dust

You know what I am? I’m a dust magnet!” enthusiastically proclaimed Pig-Pen, a beloved character in the popular comic strip, Peanuts, by Charles M. Schulz. It is said that Schulz drew inspiration for the character from observing his own son’s propensity for being surrounded by dirt1. Indeed, if you take a magnifying glass to inspect the air around your body, you will find millions of tiny airborne particles floating about. While Schulz may not have been an aerosol scientist, his portrayal of Pig-Pen as being perpetually enveloped by a cloud of particles is quite accurate.

Our activity patterns and movements indoors are responsible for creating personal clouds of dust. As we walk across the carpet or move in bed, we continually stir-up indoor dust – complex deposits of settled particles and their associated biological, chemical, and elemental material. This process, referred to as resuspension, is a major source of coarse-mode (> 1 μm) particles in our homes and offices, particularly particles of biological origin, such as bacteria, fungi, and allergens.

The quality of indoor air can be significantly influenced by human-driven resuspension of settled dust. An adult walking across the floor can resuspend 10 to 100 million particles per minute2, while tossing and turning on a mattress can stir-up similar levels of microbialladen dust3. The episodic release of dust to air is an inherently transient process, changing minute by minute due to human occupancy and movement patterns.

While we have insights into how adults kick-up particles indoors, we know comparatively less about how small infants resuspend dust. As toddlers crawl, play, learn to walk, and move during sleep we would expect them to generate their own personal dust clouds (Figure 1). Given the close proximity of their breathing zones to flooring and bedding surfaces, they are likely to be exposed to elevated concentrations of resuspended particles in their near-surface microenvironments. Resuspension may contribute meaningfully to early childhood inhalation exposures to the microbial and allergenic content of indoor dust. Such exposures can play a significant role in both the development of, and protection against, asthma, hay fever, and allergies.

Working with microbiologists and aerosol scientists in Finland, my research group recently published two of the first studies investigating dust clouds around crawling infants4, 5. To characterize the infant Pig-Pen effect, we developed a simplified mechanical crawling infant that bravely explored the particle plumes released from carpets. We used a laserinduced fluorescence (LIF)-based aerosol instrument to monitor biological particles in the infant dust clouds in real-time, along with off-line DNA-based analysis to probe specific bacterial and fungal taxa. We discovered that the crawling motion of an infant delivers a substantial number of resuspended particles to their breathing zones (Figure 2), with concentrations ranging from 50 to 600 μg/ m3(number range of 0.5 to 2 cm-3). Infants create very concentrated clouds of dust around themselves, with breathing zone concentrations roughly ten times greater than those in the bulk air of the room.

Crawling-induced resuspension is a highly transient process, as illustrated in the size distribution time-series plot of Figure 2. An abrupt burst of resuspended fluorescent biological aerosol particles in the infant breathing zone can be observed at the onset of crawling. The particle concentration then fluctuated with respect to time during the remainder of the resuspension period and decreased rapidly following the cessation of crawling. The accelerated decay in particle concentrations post-crawling suggests that an infant will receive much of their exposure to self-induced resuspended dust during periods where they are actively engaged in locomotion.

We found most of the resuspended particles to be larger than 1 μm in diameter. The size distributions exhibited a prominent mode between 3 and 5 μm, while a partial second mode was observed Figure 1. Infant dust clouds. Clouds of dust By Brandon E. Boor, Ph.D.A, B A. Lyles School of Civil Engineering, Purdue University, 550 Stadium Mall Drive, West Lafayette, IN 47907 B. Ray W. Herrick Laboratories, Center for High Performance Buildings, Purdue University, 177 South Russell Street, West Lafayette, IN 47907 Featured speaker: #TECH2019 www.nafahq.org 5 for particles greater than 10 μm. Given the results of our DNA-based analysis, we believe the 3 to 5 μm mode is likely comprised of bacterial cell agglomerates. For the particular carpet samples studied, the most abundant bacterial genera in resuspended dust included: Oxalobacteraceae gen., Acinetobacter, Paracoccus, Corynebacterium, Micrococcus, Propionibacterium, Staphylococcus, Streptococcus, Clostridium, and Sediminibacterium.

The detailed size-resolved concentration data enabled us to predict how many resuspended biological particles deposit in the infant respiratory system per unit time crawling. In one minute of crawling across a carpet, on the order of 1,000 to 10,000 resuspended particles will deposit in the infant respiratory system. Infants will receive much of their inhaled dose in their lower airways – the tracheobronchial and pulmonary regions of their lungs.

Much like Pig-Pen, babies are surrounded by clouds of dust they resuspend from indoor surfaces. As house dust is heavily enriched with an amazing diversity of microorganisms, much of the resuspended particles are of biological origin. Understanding sources of indoor particles, and their contributions to human exposure, is an important step in working towards indoor environments that promote human health and well-being.

Pugh, T. (2017). Exploring a Beloved Peanuts Character: New Exhibition at the Charles M. Schulz Museum. Press release by the Charles M. Schulz Museum and Research Center: June 28, 2017.
Qian, J., Peccia, J., and Ferro, A.R. (2014). Walking-Induced Particle Resuspension in Indoor Environments. Atmospheric Environment. 89:464-481.
Boor, B.E., Spilak, M.P., Corsi, R.L., and Novoselac, A. (2015). Characterizing Particle Resuspension from Mattresses: Chamber Study. Indoor Air. 25(4):441-456.
Wu, T., Täubel, M., Holopainen, R., Viitanen, A.-K., Vainiotalo, S., Tuomi, T., Keskinen, J., Hyvärinen, A., Hämeri, K., Saari, S.E., and Boor, B.E. (2018). Infant and Adult Inhalation Exposure to Resuspended Biological Particulate Matter. Environmental Science and
Technology. 52:237-247.
Hyytiäinen, H., Jayaprakash, B., Kirjavainen, P., Saari, S.E., Holopainen, R., Keskinen, J., Hämeri, K., Hyvärinen, A., Boor, B.E., and Täubel, M. (2018). Crawling-Induced Floor Dust
Resuspension Affects the Microbiota of the Infant Breathing Zone. Microbiome. 6:25.

Author: Brandon E. Boor, Ph.D. (A, B)

A. Lyles School of Civil Engineering, Purdue University, 550 Stadium Mall Drive, West Lafayette, IN 47907
B. Ray W. Herrick Laboratories, Center for High Performance Buildings, Purdue University, 177 South Russell Street, West Lafayette, IN 47907

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Making Polling Places Safer

nafa@nafahq.org — Thu, 29 May 2025 14:27:03 +0000

Making Polling Places Safer

May 29, 2025

The Latest Recommendations from the ASHRAE Epidemic Task Force

As election season continues throughout the nation during the pandemic, the ASHRAE Epidemic Task Force is offering HVAC and water supply system guidance for polling places.

ASHRAE’s Building Readiness guidance provides practical information and checklists to help minimize the chance of spreading SARS-CoV-2, the virus that causes COVID-19.

“Protecting our voters and poll workers from increasing the spread of COVID-19 at polling places is essential to protecting the health, welfare and safety of the entire population,” said Dennis Knight, ASHRAE Epidemic Task Force vice chair. “Many different HVAC system types are used in polling places, so adaptation of these guidelines to specific cases is necessary.”

Here is a summary of key general recommendations related to HVAC and water supply systems for polling places:

Space Selection: Select a space with a larger area for people to spread out, and if possible, a high ceiling to provide more volume for dilution. Consider space with operable windows if there are potential ventilation issues.
Inspection and Maintenance: Consider assessing the condition of systems and making necessary repairs. All building owners and service professionals should follow ASHRAE Standard 180-2018 “Standard Practice for the Inspection and Maintenance of Commercial HVAC Systems.”
HVAC Operation: The HVAC and toilet exhaust systems should be running when the space is occupied. If the HVAC system cycles on/off with the thermostat, consider running the fan constantly during occupied hours. If toilet exhaust is controlled by manual switches, leave the fan running for 20 minutes after use, or consider setting the switch to “on” and use signage that directs not to change the setting.
Ventilation: A good supply of outside air, in accordance with ASHRAE Standard 62.1-2019, to dilute indoor contaminants is a first line of defense against aerosol transmission of SARS-CoV-2. Pre- and post-occupancy purge cycles are recommended to flush the building with clean air. If the polling place is not ventilated or poorly ventilated and filter efficiency is not good, consider opening doors and windows, and consider re-locating all voting to the outdoors.
Air Distribution: Air flow distribution should not cascade air from the face of a person onto others, so take care in using personal fans.
Filtration: Use of at least MERV-13 rated filters is recommended, if it does not adversely impact system operation. If MERV-13 filters cannot be used, including when there is no mechanical ventilation of a space, portable HEPA air cleaners in occupied spaces may be considered. Also consider portable air cleaners in locations with more vulnerable staff. Making Polling Places Safer The Latest Recommendations from the ASHRAE Epidemic Task Force Photo by Element5 Digital from Pexels www.nafahq.org 19 Thank you to all the NAFA Members who participated in our survey on possible upcoming webinars NAFA will offer. Here are the top 5 topics you want to hear about: NAFA survey - top 5 requested webinar topics
Air Cleaning: Air cleaners such as germicidal ultraviolet air disinfection may also be considered to supplement ventilation and filtration. Technologies and specific equipment should be evaluated to ensure they will effectively clean indoor air without generating additional contaminants or negatively impacting space air distribution by creating strong air currents.
Temperature and Humidity: It is desirable to set the thermostat at the higher end of the comfort zone, 75- 78ºF and maintain relative humidity between 40-60%.
Energy Use Considerations: In selecting mitigation strategies, consideration should be given to energy use as there may be multiple ways to achieve performance goals that have greatly different energy use impact. Control changes and use of energy recovery to limit or offset the effect of changes in outdoor air ventilation rate and filter efficiency may reduce or offset energy and operating cost penalties.
Water System Precautions: Buildings that have been unoccupied could have stagnant water, and water systems should be flushed to remove potential contaminants. Utilizing ASHRAE Standard 188 and Guideline 12 can help minimize the risk of water-borne pathogens such as legionella.

Epidemic Task Force Guidance for Polling Places
https://tinyurl.com/ASHRAEVote

“The task force’s approach to protecting indoor air quality in polling place is practical, and can help safeguard voters, poll workers and other building occupants as most sites are shared locations that serve many different purposes,” said Luke Leung, ASHRAE Epidemic Task Force commercial/retail team lead.

ASHRAE’s Epidemic Task Force has developed guidance and building readiness information for different operating conditions and several building types, including commercial, residential, educational, and healthcare facilities.

To view complete guidance on HVAC and water supply systems in polling places, along with other COVID-19 resources, visit ashrae.org/COVID-19.

The post Making Polling Places Safer appeared first on National Air Filtration Association.

Guidance for Dealing with Wildfire Smoke

nafa@nafahq.org — Wed, 21 May 2025 19:38:27 +0000

Guidance for Dealing with Wildfire Smoke

The frequency of wildfires and the range of their impact is on the increase. What has often been considered a west coast phenomenon made its presence felt on the east coast starting the week of June 4^th, 2023, when the prevailing wind patterns brought wildfire smoke down from Canada as far south as the Carolinas.

Some of the consequences of wildfires include a reduction in the quality of both indoor and outdoor air, a reduction in water quality, public health issues that are more acute for those with asthma and other pre-existing medical issues, damage to the ecosystem, and negative economic impact to local economies.

Many communities are exposed to wildfire smoke for days, weeks, or even months at a time. The smoke can easily enter the indoor environment through natural ventilation, infiltration, and mechanical ventilation. The primary contaminant of wildfire smoke is particulate matter. Wildfire smoke can contain up to 90% of PM_2.5. In addition to the particulate matter, wildfire smoke contains gas-phase contaminants such as ozone, sulfur dioxide, carbon monoxide, carbon dioxide, and volatile organic compounds.

Most public health guidance over the last five years advises staying indoors and closing all windows and doors during a wildfire event. In 2020, the EPA worked with the National Institute of Standards and Technology (NIST) to propose that the American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE) develop a wildfire smoke guideline.

This guideline was released in February 2021 and it focuses on reducing fine particle (PM_2.5) exposures from smoke in commercial buildings, schools, healthcare facilities, multi-unit residential structures, and similar buildings.

Based on this guidance, there are steps that can and should be taken in advance of a wildfire event. These steps include, but are not limited to the following:

Buying supplies early (filters and portable air cleaners)
Evaluating your HVAC system to determine if it can handle a higher efficiency filter
Reviewing the building envelope, weatherizing it, and sealing it as needed
Conducting a full maintenance check on the HVAC system and making repairs as needed
Checking for the ability to reduce the outdoor air volume while maintaining positive pressure
Investigating the addition of supplemental filtration at intakes or in the occupied spaces
Consulting a qualified HVAC professional where necessary
Installing air monitors with a PM₅ sensor and pressure sensors

Once a wildfire event begins, there are an equal number of actions to take. The actions to take during an event include:

Maintaining supplies (filters and portable air cleaners)
Conducting frequent maintenance checks on the HVAC systems and all filters
Limiting outdoor air intake while maintaining adequate air flow to maintain positive pressure
Adding supplemental filtration where possible
Utilizing MERV 13 or higher filters
Utilizing combination particulate/gas-phase filters
Monitor the PM2.5 concentration in the occupied areas of a building and/or at air intakes
Use differential pressure sensors to measure the pressure difference between the building interior and the outdoor air
Add portable air cleaners with HEPA filters as needed

If portable air cleaners are used, make sure that the air cleaner is rated by The Association of Home Appliance Manufacturers (AHAM). Units with a sufficient smoke clean air delivery rate (CADR), sized for the application, and with low noise ratings are recommended. For wildfire smoke, AHAM updated their sizing recommendation to a smoke CADR equal to the size of the room in square feet from the 2/3 the room area rule of thumb. Keep in mind that multiple air cleaners may be needed for larger rooms. Additional information on the selection and use of portable air cleaners can be found on the Environmental Protection Agency (EPA) website.

The time to act is before a wildfire event occurs. Ensure that you have a smoke readiness plan before you need one. Utilize sources such as weather websites and fire.airnow.gov for tracking wildfire events, smoke patterns, and the Air Quality Index (AQI). Use these sources to help determine when you should enact your smoke readiness plan. Additional information and guidance can be found on the NAFA, EPA, and ASHRAE websites.

Author: Dave Schaaf

The post Guidance for Dealing with Wildfire Smoke appeared first on National Air Filtration Association.

History and Future of Nanofibers in Air Filtration

nafa@nafahq.org — Wed, 21 May 2025 15:44:52 +0000

History and Future of Nanofibers in Air Filtration

What are Nanofibers?
Nanofibers are defined by being a one-dimensional fiber in length. The diameter is so small that the fiber is practically invisible to the flow of the medium being filtered. Different sources cite varying diameters that classifies a nanofiber. Are nanofibers less than 1 micron in diameter? Less than 500 nanometers? Less than 100 nanometers? One practical example I have used to illustrate the scale of a nanofiber is roughly 1000 times smaller than a piece of hair, as seen in Figure 1.

Figure 1: Size comparison of ePTFE nanofiber membrane to human hair.

Some physical property advantages that come with having nanoscale fiber diameters include high surface area to volume ratio, high mechanical strength per volume, and the ability to be highly functional. The high surface area to volume ratio allows nanofibers to make a significant impact on the filtration performance with a small amount of material weight added to the filter media. The unique air flow properties come from a phenomenon called “slip flow”, illustrated in Figure 2, that occurs when the surface of the fiber is not large enough to impact the velocity profile through the filter media.

Figure 2: Illustration of slip-flow occurring on nanofiber surface in an airstream.

History
The history of what eventually led to the current state of nanofiber production can be traced as far back as the 1600’s. Scientists at that time observed how liquids behaved in an electric field, particularly the fact that the electric field would break the surface tension of the round liquid droplet and form a cone shape. This cone would eventually come to be known as a Taylor cone. In the 1800’s an English physicist named Lord Rayleigh observed liquid droplets ejecting from this Taylor cone. When the liquid is a polymer solution, the polymer chains entangle and link these droplets to form a continuous fiber being ejected from the Taylor cone. The first patent for producing fibers in this way was granted in the early 1900’s. In the 1990’s, the term “electrospinning” was coined and research accelerated, especially by a group at The University of Akron led by Professor Darrell Reneker that was on the forefront of studying the properties of and applications for electrospun nanofibers.

Figure 3: Illustration of how a liquid droplet deforms into a cone and ejects a fiber jet in an electric field.

Another example of a nanofibrous media was discovered in 1969 when Bob Gore discovered the properties of stretching (or expanding) polytetrafluoroethylene (PTFE) tape, creating ePTFE. Expanding the tape didn’t immediately cause a break and close observation of the stretched material revealed a network of ultra-fine fibers. This material was initially used in fabrics but applications in filtration started in the 1970’s.

Current State of Nanofibers
One air filtration application that has been successfully using nanofibers is ePTFE media in HEPA and ULPA filters. Slip-flow, enhanced particle capture capabilities, and higher mechanical strength properties have led to the development of HEPA and ULPA filters with lower resistance to air flow at the same filter efficiency class and configuration when compared to conventional microglass HEPA and ULPA filter media.

Figure 4: Comparison of typical microglass HEPA filter media (left) and ePTFE HEPA filter media (right)

The two SEM micrographs in Figure 4 show that the structure of the ePTFE media consists of smaller fibers and pores, which helps increase the filter efficiency with reduced pressure drop. This combination of properties also leads to the most penetrating particle size (MPPS) of the filter media to be smaller than that of traditional microglass filter media, which will lead to a more efficient filter at most particle sizes, as seen in Figure 5.

Figure 5: Filter efficiency at most penetrating particle size (MPPS) for microglass and ePTFE filters

As Table 1 displays, the ePTFE filter media has about half the resistance to air flow as microglass filter media, which leads to the construction of a filter of the same configuration with about half the resistance.

These properties are highly beneficial for filtration applications because end users are always looking for more durable filter media that has a lower pressure drop, however there are some downsides for nanofiber media. One downside is that nanofibers in filtration act as a membrane, or a barrier, so that the particulate being filtered has a very low probability of passing through to the other side. Traditional filter media has depth to it, so particulate has space to accumulate within the filter media. This downside is not of concern for HEPA filtration, where the HEPA filter is a “last line of defense” to ensure a clean space on the downstream side of the filtration system. HEPA filter applications usually have multiple levels of prefiltration upstream to ensure premature loading of the HEPA filter does not occur. However, nanofibers in HVAC filter efficiency levels (MERV rated by the ASHRAE 52.2 test standard) have shown weaknesses when being tested under standard lab test conditions.

Figure 6: comparing a MERV 7 filter before and after the addition of a nanofiber layer.

As seen in Figure 6, the addition of nanofibers can boost the efficiency a relatively low efficiency filter media (MERV 7) up to a MERV 11, which has significantly better particle capture properties, particularly with smaller particles that are of higher concern to human health. However, this benefit comes at the expense of higher resistance to air flow (two times increase, from 0.19 iwg to 0.40 iwg) and significantly lower dust holding capacity (more than ten times reduction, from 192 g to 15 g). Part of this is due to the types of dust the filters are challenged with during the lab test and how the filters are tested, there are commercially available nanofiber filters that are able to last long enough in HVAC applications, it is just that the test method isn’t kind to nanofiber filter media so it is difficult to quantify in a lab. There is also an inconsistency that can come from depositing nanofibers on a filter media surface, as seen in Figure 7.

Figure 7: Inconsistencies in nanofiber coated filter media.

The cause for the variation in nanofiber coating can come from any number of reasons, but there are ways to overcome this by protecting the nanofiber with a support media, or a scrim, that can be used to make a combination filter media. The right combination of filter media technologies can also help solve issues related to pressure drop and dust holding capacity, which leads to where we can go in the future for nanofiber technology.

The Future of Nanofibers
One particulate HVAC filter application that has seen nanofibers used successfully is in bag filters.

In this particular application the filter media manufacturer is able to add three-dimensional surfaces containing nanofibers within a thicker filter media which reduces the pressure drop penalty of using a mechanical nanofiber filter media (the initial resistance is actually less than that of a traditional microglass media bag filter of the same efficiency) and the three-dimensional media also has a high dust holding capacity, equal to or exceeding that of traditional microglass media. Due to the thickness of this type of filter media it is currently limited to bag filter or pad filter media, but these are the types of advancements that can lead to innovation in pleatable nanofiber filter media as well.

Another area that can be improved in the future is how we test filters. As mentioned previously, the current lab tests and especially loading dusts don’t exactly mimic “real-life” conditions the filter will be exposed to in application. Most particles the filters will be seeing under normal atmospheric air conditions are less than 1 micron, but ASHRAE and ISO loading dusts consist mainly of particles larger than 1 micron and even as large as 100 microns. With recent events, such as COVID and wildfires, drawing more attention to air quality, there is a need for innovation in how we test and use air filters. ASHRAE is funding research for investigating a lab filter loading test that better matches atmospheric dust loading conditions, and filter application standards are putting a larger emphasis on using higher efficiency filters. This combination of standards activity and research will drive innovation to develop a better filter that can maintain a high efficiency rating and perform well in HVAC systems.

Author: Jon Rajala, Ph.D., R&D Manager, AAF International

The post History and Future of Nanofibers in Air Filtration appeared first on National Air Filtration Association.

Molecular Filtration

nafa@nafahq.org — Mon, 19 May 2025 19:06:14 +0000

Molecular Filtration

May 19, 2025

History
The first documented use of activated carbon (known as charcoal) can be traced back to around 3750 B.C. when it was first used by the Egyptians for smelting ores to create bronze. By 1500 B.C. the Egyptians had expanded its use to healing intestinal ailments, absorbing unpleasant odors, and for writing on papyrus. By 400 B.C., the Ancient Hindus and Phoenicians recognized the antiseptic properties of activated charcoal and began using it to purify their water.

Between 400 B.C. and the 1800s, activated charcoal was used to remove odors from wounds, preserve water during ocean voyages, and to treat battle wounds by the military by removing toxins.

The earliest use of activated carbon for gas-phase contaminant removal dates to 1854, when a Scottish chemist invented the first mask that utilized activated carbon to remove noxious gases. Wood was originally used as the base material for gas masks since it was good at capturing poisonous gases when converted to activated carbon. By 1918, it was determined that shells and nuts converted to activated carbon performed even better than wood.

Around this same time, activated carbon began to be produced on a large scale and its use spread to decolorization in the chemical and food industries. In the later 1900s, other industries such as corn and sugar refining, gas adsorption, alcoholic beverage production and wastewater treatment plants began to use activated carbon.

Today, activated carbon is available in many different shapes and sizes and its applications are growing every day. For air filtration, the most common types of activated carbon are granular activated carbon (GAC), pelletized activated carbon (PAC), and structured activated carbon. In addition, other substrates such as alumina and zeolite are used in lieu of activated carbon due to their tremendous pore structures. The most common applications of these different media types include corrosion control, odor control, and protection from toxic gases.

What are Gaseous Contaminants?
Gaseous contaminants are undesirable airborne molecules mixed with the normal molecular oxygen and nitrogen in the atmosphere. Because of their molecular size, in the sub-nano range, they are not visible. Also not visible, but present in the air, is desirable molecular water, which is referred to as humidity. Some common offensive undesirable gaseous contaminants are hydrogen sulfide, the rotten egg smell, or skatole, the dirty diaper smell. Many gases that evolve from combustion are contaminants, such as carbon monoxide, oxides of nitrogen, oxides of sulfur, and polyaromatic hydrocarbons.

Size – Gaseous and Particulate Contaminants
The graphic in Figure 1 illustrates the relative size differences of airborne contaminants. Some particulate contaminants, such as viruses and bacteria, although not visible, have a mass size large enough to be filtered with specialized particulate filters. Gaseous
contaminants can only be effectively removed using molecular gas-phase filtration technologies.

Figure 1

Types and Sources of Gaseous Contaminants
Gaseous contaminants are generally classified as Odorous, Corrosive, or Harmful/Toxic. Examples of their sources are shown in Figure 2.

Often, contaminants can be classified in more than one category. One example of this is hydrogen sulfide (H2S) which is both corrosive and odorous.

Control of Gaseous Contaminants
There are various ways to control gas-phase contaminants. One method is source control wherein the source of the contaminant(s) is relocated or eliminated. A second technique is ventilation where large amounts of fresh air are added to the contaminated air to dilute the contaminants. Often, neither of these control methodologies will work. In these cases, gas-phase filtration systems must be utilized. A schematic is shown in Figure 3.

Figure 3

Gas-phase filtration devices are used in combination with particulate filters to remove gaseous contaminants. A particulate filter is always required upstream of the gas-phase filter to ensure that all dirt and dust is removed from the airstream. A particulate, final filter is recommended downstream of the gas-phase filter when the air is going to be recirculated back into an occupied space. The purpose of this particulate filter is to capture any dust that might come off the chemical media in the gas-phase filter. When the air exhausted to atmosphere, there is not a need for a final filter.

Selecting Gas-phase Filtration Devices
Choosing the correct chemical media type and the correct chemical media delivery product is a daunting task. There is a lot of information that must be gathered first such as the contaminants of concern (COC) the concentrations of the COC, the air volume, the desired media life, the space available, and more. A good starting point is completing an application questionnaire like Figure 4 below to document as much of this information as possible.

The gathering of the data is the first step in determing the correct media type. In most applications, there is one chemical media type that will work best. There are times, however, when more than one media type will work as well as times when more than one media type is required as part of the solution due to the list of contaminants that need to be removed. To further complicate matters, there are multiple chamical media delivery devices that are available and most of the time, more than one of those devices will work. The amount of space that is available along with number of media types required are the two main factors that will determine which delivery device will best solve the application at hand. Due to this complexity, it is recommended that you reach out to your local filtration specialist to assist you with making the proper selction.

The Minimum Viable Product
The minimum viable product is usually determined by the customer or end user and is defined as the minimum acceptable service life of the filtration device before the chemical media removal capacity is exhausted. Figure 5 below demonstrates how there is usually more than one viable product solution for most gas-phase applications.

Figure 5

The table shows the expected life in months versus the contaminant challenge for various gas-phase filtration products. The gray boxes show acceptable products for roughly a three-month minimum life and the pink boxes show acceptable products for a six-month minimum life. When evaluating a gas-phase application, it’s important to understand the most important requirements for that application such as first cost, replacement cost, ease of replacement, and space available so the best product value is chosen.

Remaining Life Analysis
When the best chemical media has been determined and the filtration device has been selected, the question of how long this filtration device will last often comes up. The manufacturer of the filtration device should be able to provide an estimate of expected life of the chemical media. To verify that estimate, the remaining life of the chemical media can be tested. Remaining life analysis compares the known, initial capacity to the current capacity of chemical filtration media that is installed in filtration systems. The information obtained from this testing can be used to confirm system performance, determine the media replacement schedule, and to assist with inventory control of replacement media. Replacing media based on testing maximizes the media life, reducing the total cost of system ownership.

Author: Dave Schaaf

The post Molecular Filtration appeared first on National Air Filtration Association.

Don’t Let Your Customers Forget

nafa@nafahq.org — Mon, 19 May 2025 18:37:27 +0000

Don’t Let Your Customers Forget

May 19, 2025

I have been in the Indoor Air Quality industry for the past 15 years and have experienced other pandemics such as Bird Flu, Swine Flu, MERS, SARS, Ebola, and the Zika virus and one common theme occurred after each pandemic slowed and passed - people forgot about air quality! People went back to their daily routines, stopped protecting themselves, stopped worrying about a potential deadly disease, stopped equipping their facilities to protect occupants, stopped maintaining Indoor Air Quality equipment they installed to help with a pandemic.

Repeating the pattern?
We are now coming out of a 100-year Global Pandemic of SARSCoV 2 and I am afraid we are seeing the same pattern begin to happen. While many schools and universities continue to equip their AHU and RTU with MERV 13 filters, many commercial office buildings, religious buildings, and manufacturing facilities have gone back to MERV 8 and are not actively promoting a higher level of Indoor Air Quality. While I recognize there is a vaccine for COVID 19 which will cause many to relax, the threat of a new pandemic looms on the horizon. Pandemics occur approximately every 5-9 years and if we fail to stay vigilant and prepared, we will not be ready for the next one.

Micro-organisms have been on the earth for hundreds of millions, potentially billions of years. Humans can't beat them; we must learn to live with them and proactively protect ourselves from them. Outside of vaccines, let’s discuss what facilities can do to protect their employees, occupants, patients, or customers from airborne infectious aerosols and be better prepared for the next pandemic.

For the last few decades, we designed our buildings to save energy and protect the HVAC equipment. In many cases protecting the equipment doesn’t necessarily protect the occupants. As air filtration and attention to Indoor Air Quality has heightened, we are starting to implement Indoor Air Quality measures that will protect both the occupants and in turn, the equipment. Humans are our most precious resource and building owners, designers, and maintenance personnel should change their perspective on Indoor Air Quality and understand how important it is for the health, safety, and productivity of tomorrow’s buildings. We as Air Filtration and Air Quality professionals should continue to push for higher standards, push for higher education and hold our customers accountable for their air quality. Given our technological advancements in filtration, air cleaning and air disinfection, there is no excuse to not implement permanent improved measures moving forward.

In the latest edition of ASHRAE Journal Dec 2022, an article titled “Developing Indoor Air Quality Standards: Reflecting on a White House Summit” (see page 8) outlines how IAQ experts are rapidly working on implementing lessons learned from the COVID pandemic. This time could be different, the IAQ experts will not allow the public to forget.

In the first sentence, the White House Coronavirus Response coordinator emphasizes that there are two choices – prevention or repair. Essentially, America can help prevent people from getting sick or spend extra money trying to deal with a larger sick population. We all agree that prevention is a much better solution, but Cont' d on next page implementing it is a different problem. It comes down to funding, education, and implementation. I can’t help with the funding portion of the problem, but I can help with education and implementation. Let’s discuss in more detail how ASHRAE recommends facilities to prepare for the next pandemic.

The American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) tasked former ASHRAE President William Bahnfleth, PhD with the goal of putting together a task force to study and recommend guidelines for Infectious Aerosol mitigation during the start of the COVID pandemic. Dr. Bahnfleth has formed a team of top professionals in the Heating, Ventilation and Air Conditioning (HVAC) Industry and with combined knowledge of the history of pandemics such as SARS, MERS, Bird flu, swine flu, and Zika, the task force knew very quickly that this novel coronavirus, SARS CoV 2 would be spread via airborne aerosols. Thus, the Epidemic Task Force recommends five core strategies to help limit the spread of airborne infectious aerosols within a building.

Upgrade filtration to MERV 13 or better where possible
Commissioning – building tune-up
Increase ventilation when possible
Control humidity 5. Utilize UVGI or portable air cleaner

Let’s briefly cover each recommendation to help NAFA members provide more detail and education to Facility Managers, Chief Engineers, Maintenance Technicians and Mechanical Engineers.

Upgrade filtration to MERV 13 or better where possible
ASHRAE Standard 62.1 generally requires filters in HVAC systems of at least MERV 8. As you can see in the chart below, a MERV 8 filter has no performance benefit on a particle or aerosol in the 0.3-1.0 um size.

Additionally, there is an exponential difference in performance between a MERV 8 and a MERV 13 filter within the E2 aerosol and particle range. SARS CoV 2 is transmitted via aerosols as we talk, breathe, cough or sing. These aerosols range from 10 to smaller than 1 um with the target aerosol being in the E2 – 1-3 um range. These aerosols or particulate could enter deep into our lungs causing respiratory issues. Many IAQ experts are pushing for the standard to be raised from MERV 8 to MERV 13. As more data and research into E2 size range particles are performed, expect the conversations to increase concerning the greater implementation of MERV 13 filters. Now, this recommendation is not without one caveat. In some cases, the filters’ air resistance or how much force it takes to push or pull air through the filter is too great for the HVAC unit’s fan or compressor due to several factors such as age of unit, type of motor or type of filter rack. There are a few ways to overcome those obstacles such as switching to a new 6 NAFA Air Media filter rack accommodating a 2” or 4” filter to help lower the pressure drop. Secondly, utilize multiple stages of filtration or add additional air cleaning products such as UVGI in the air handler to aid in the disinfection of mold, virus, and bacteria. Lastly, upgrading the fan motor to handle more static pressure could be another great solution. For more information refer to the ASHRAE position document on Filtration and Air Cleaning 2015 and ASHRAE Position Document on Indoor Air Quality 2021.

Commissioning – building tune up
A recent study of the U.S. Government Accountability Office report found that more than 40% of school districts required replacement or upgrade of their HVAC systems.1 Many older facilities will have an inadequate fan, condenser motors or duct dimensions to utilize a MERV 13 filter. These facilities are highly recommended to upgrade their systems where possible and utilize the ASHRAE retro-commissioning process to achieve the desired performance. More information can be found in the ASHRAE 2008 document Indoor Air Quality Guide: Best Practices for Design, Construction, and Commissioning.

Increase ventilation where possible
The third core recommendation for infectious aerosol control is to increase the percentage of ventilation within the building. Increased ventilation rates can be achieved by introducing more outside air, by recirculating air through a MERV 13 filter or utilizing other treated air. Some climates are better suited for increased outside air; however, buildings must be mindful of their energy usage and choose the best ventilation method as dictated by their climate and humidity. In many studies, treated outdoor air ventilation rates have shown a positive correlation with indoor air quality, including reduced sick building syndrome symptom, reduced absenteeism, better task performance and increased learning performance (Sundell et. Al. 2011) Likewise, higher ventilation rates are associated with lower incidence of airborne diseases. For additional details on recommended ventilation measures, see the ASHRAE position on Infectious Aerosols: October 13, 2022.

Control humidity
The fourth core recommendation would be to control humidity within a building, with an objective of maintaining a 40% - 60% humidity level. Research indicates that maintaining the relative humidity between 40% - 60% decreases the infectivity and reduces the viability of many airborne infectious aerosols. In addition, peak comfort for the occupants can also be achieved within this recommended humidity range. As with the other recommendations, if humidity cannot be maintained between 40% - 60%, then other mitigating measures should first be implemented.

Utilize UVGI or a portable air cleaner
The fifth core recommendation is to utilize an Ultraviolet Germicidal Irradiation system (UVGI) in the HVAC unit or a portable air cleaner. Ultraviolet Germicidal irradiation (UVGI) has been utilized for over 100 years in both the water and air disinfection industries and has been proven to disinfect mold, virus and bacteria both in the airstream and on a surface when sized correctly. UVGI is a top recommendation when dealing with any airborne or surface borne micro-organisms. It will reduce the bioburden without any increase in pressure drop. A building can also use a portable air cleaner such as the Rosenthal-Corsi box or a commercially available air cleaner utilizing a HEPA filter. Portable air cleaners can be placed anywhere inside a room and can provide additional air cleaning to the forced air system or replacement air cleaning if no forced air system is being utilized. Higher numbers of air changes per hour will perform better over time across all particle sizes than simply looking for a unit with a HEPA filter and a low-speed fan. Additionally, the status of air cleaning technologies is reviewed in the ASHRAE Position Document on Filtration and Air Cleaning (ASHRAE 2021).

While there are additional methods to help slow the impact of infectious aerosols, we’ve only covered the core recommendations by the ASHRAE Epidemic task force. Please utilize these as beginning discussions with your customers. These are not hard and fast rules and if you’ve been in the filtration industry for any length of time, you know there are always exceptions. Let’s instead focus on education and helping prepare your customers for the next pandemic. It is our responsibility as air quality professionals to prepare, preach and help position our current and future generations actions to diminish the next airborne pandemic.

References

U.S. Government Accountability Office. 2020. “K-12 Education: School Districts Frequently Identified Multiple Building Systems Needing Update or
Replacement.” https://www.gao.gov/products/gao-20-494
The White House. October 12, 2022. White House Summit on Indoor Air Quality. https://youtube/q1HCG1aXaBg
Burley, Ph.D., P.E., Brendon. 2022 “Developing Indoor Air Quality Standards: Reflecting on a White House Summit.” ASHRAE Journal 64:.
ASHRAE Epidemic Task Force. 2021. “Core Recommendations for Reducing Airborne Infectious Aerosol Exposure. https://www.ashrae.org/file library/technical resources/ covid-19/core-recommendations-for-reducing-airborne-infectious-aerosol-exposure.pdf
ANSI/ASHRAE/ASHE Standard 62.1-2002. Ventilation and Acceptable Indoor Air Quality.
Allen J.G., A.M. Ibrahim. 2021. Indoor Air Changes and Potential Implications for SARS-CoV-2 Transmission. JAMA 2021 25.325(20):2112-2113. Doi: 10.1001/jama.2021.5053
ASHRAE., 2008. “Indoor Air Quality Guide: Best Practices for Design, Construction, and Commissioning.” https://iaq.ashrae.org/
ASHRAE.2019a. Chapter 62, “Ultraviolet Air and Surface Treatment.” In ASHRAE Handbook – 2019 HVAC Applications. Peachtree Corners, GA: ASHRAE
ASHRAE. 2021. ASHRAE Position Document on Filtration and Air Cleaning. Peachtree Corners, GA: ASHRAE.
ASHRAE Position Document on Indoor Air Quality. 2020. ASHRAE., https://www.ashrae.org/file library/about/positions documents/pd_indoor-air-quality-2020-07-01.pdf
ASHRAE. Positions on Infectious Aerosols. ASHRAE., 2022. https://www.ashrae.org/File%20Library/About/Position%20Documents/PD_-Infectious-Aerosols-2022.pdf
Sundell, J., H. Levin, W.W. Nazaroff, W.S. Cain, W. J. Fisk, D.T. Grimsrud, F. Gyntelberg, Y. Li, A.K. Persily, A.C. Pickering, J.M. Samet, J.D. Spengler, S.T. Taylor, and C. J. Weschler, 2011. Ventilation rates and health: Multidisciplinary review of the scientific literature. Indoor Air 21(3):191-204. https://doi.org/10.1111/j.1600-0668.2010.00703.x.
Jones, E.R., M.V. Rainbold, L.C. Marr. D. Michaels, et al. 2022. The First Four healthy Building Strategies Every Building Should Pursue to Reduce Risk from COVID-19. Lancet COVID-19 Commission Task Force on Safe School, Safe Work, Safe Travel. https://covid-
19commission.org/safe-work-travel.
Wyon. D.P., P. Wargocki. 2013. “How indoor environment affects performance.” ASHRAE Journal 55.46-53
World Health Organization. 2021. WHO Global Air Quality Guidelines. Particulate matter (PM2.5 and PM10), ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide. WHO. Geneva. Switzerland.

Author: Keith Jordan is President of Colorado Air Filter

The post Don’t Let Your Customers Forget appeared first on National Air Filtration Association.

How do I Best Filter My Recycled Dust Collector Exhaust?

nafa@nafahq.org — Wed, 14 May 2025 19:32:38 +0000

How do I Best Filter My Recycled Dust Collector Exhaust?

May 14, 2025

A Glimpse Into the Standard Setting Process of the new NFPA 660 Consolidated Standard for Combustible Dusts

The National Fire Protection Agency (NFPA) standard on the appropriate media to use when recycling indoor air from dust collectors is a topic that just begins to scratch the surface on some of the challenges the standards development agency has faced during its current process of merging six separate NFPA combustible dust standards into one comprehensive standard, NFPA 660 Standard for Combustible Dusts, which is set to be released in early to mid 2025. This article will share some insight on this standard setting process through a close up look on the specific standard of the recycling air indoors from dust collectors. The six standards set to be consolidated are the following:

NFPA was founded in Quincy, MA in 1896 and for more than 125 years has been writing safety standards with the primary mission to help save lives and reduce loss. This has been accomplished through the development of safety code by the expertise of its more than 250 committees and over10,000 global volunteer committee members. These members include architects, analysts, engineers, government officials, manufacturers, first responders, and many others. The national electric code (NEC) is one of many standards that NFPA authors and maintains. ^1.

Six separate combustible dust standards have been independently published for many years, with the first NFPA standard on combustible dust dating back to the early 1920’s in response to a series of fatal combustible dust accidents in the agricultural and food processing industries. Through the years, these independent standards became harder and harder for users to navigate and apply consistently. Approximately 5 years ago, a decision was made to begin a merge process with the objective to make easier the application of the standards to reduce risk of often fatal accidents involving combustible dust explosions ^2.

Consolidating these standards has been a herculean task, consuming its many volunteer committee members now for years. This effort has included analyzing, combining, and debating hundreds of pages of guidance across the six standards on combustible dust safety. The distillation process of many years of effort and hard-fought advances in combustible dust safety has been challenging to say the least.

An example of one topic in particular that demonstrates the challenge of creating shared language around a single standard has been the guidance involving the indoor recycling of exhaust air from dust collectors. The benefits of recycling filtered air from a dust collector are clear:

No reconditioning of air required. This amounts to a significant amount of cost savings through saving energy to heat or cool replacement air, particularly in more variable climates.
No burdensome permitting required. Exhausting outdoors in most if not all municipalities requires facilities to go through an air permitting process. Depending on the local, state, and national regulations where the facility is located this can be quite onerous, expensive, and time consuming for organizations to endure.
No pressure re-balancing required. Exhausting large amounts of air creates unwanted negative pressure inside facilities that needs to be balanced with additional air. If the amount of air being exhausted outside a facility varies over the course of operations, this becomes an ongoing operational challenge.

The hazards of recycling exhaust air from a dust collector are also clear – when filtering combustible dust in a dust collector, there is considerable risk of creating an explosive environment if the dust collector equipment and its respective integral filtration is not properly managed and consistently monitored by operators. A few of those risks include:

Fugitive dust accumulation. An over-accumulation of combustible dust inside a collector due to not properly managing filter changes can quickly result in an abundance of fuel that, when dispersed, could easily result in an explosive dust cloud.
Filter breach. If filters are not properly installed or managed, a filter breach can occur. This could cause combustible dust to bypass the filter and then be widely exhausted back into a facility. This dust cloud dispersion is a key ingredient in the recipe for a deflagration or explosion event.
Miscalculation of particle size. If the application being addressed is producing particles smaller than the efficiency of the filter, this could result in small explosive particles making their way through the filter media and being exhausted back into the facility, with similar potential results as the bypass event cited in #2.

When it comes to the most effective way to specify the level of cleanliness of filtered air prior to recycling back into a facility from a dust collection system, the existing six standards offer conflicting guidance. The question is clear – what should the commonly accepted level of filtration become for the new consolidated NFPA 660 to best ensure the safety of recycled air from from dust collectors?

A task group was created and the scope defined. Our objective was to determine the best common language across the six standards that would guide users of the standard to understand how to approach handling this important facility management decision when selecting and managing dust collection systems.

The most compelling idea put forth by a task group member was to use widely accepted MERV values ^3. as a way to guide users towards the most efficient and safe approach to appropriately size filtration prior to recycling air. MERV relates to filter efficiency and could be matched to the related particle size of the material being processed to allow for maximum capture of the particular combustible dust being generated. Using common language that incorporated MERV makes a lot of sense – but unfortunately we could not gain consensus on its use within our task group.

Ultimately, we decided to use more general language that leads users to refer to the “applicable industrial hygiene exposure limits” – based on the particular application in question and materials being processed. This approach felt like a compromise. While the applicable industrial hygiene exposure limits often are very stringent, my belief is that the universally known MERV ratings are much more accessible, easier to digest, and straightforward to apply. Task group members felt like the use of MERV more applied to HVAC and not dust collection, and that the potential to overlook combustibility concerns was present if we used MERV.

At the end of the day, we achieved what we set out to do – establishing common language in the new NFPA 660 that provides guidance on how to approach filtration of recycled exhaust air from a dust collector. What was also learned was that consensus and common decision-making when developing standards is often challenging, slow process. The goal, however, of keeping facilities safe and giving users a guide to do so has been maintained. If you encounter combustible dust in your environment, keep an eye out for the release of 660 coming soon to your local code enforcement officials.

Footnotes:

National Fire Protection Agency, https://www.nfpa.org/About-NFPA
Dust Safety Science, https://dustsafetyscience.com/nfpa-660-standard-for-combustible-dust/
United States Environmental Protection Agency, https://www.epa.gov/indoor-air-quality-iaq/what-merv-rating

Author: Dan Prather, President of DualDraw, LLC

The post How do I Best Filter My Recycled Dust Collector Exhaust? appeared first on National Air Filtration Association.

The Gears of Grategy®: Innovating Air Filtration Workplace Culture

nafa@nafahq.org — Wed, 14 May 2025 19:15:50 +0000

The Gears of Grategy®: Innovating Air Filtration Workplace Culture

May 14, 2025

In the wake of the pandemic, the air filtration industry faces a unique set of challenges and opportunities within an increasingly employee-driven and competitive market. The adage, "Times are changing," rings truer than ever, marking a definitive shift from the “good ole days” of 2019. This article will give air filtration professionals the strategies needed to keep their top talent from becoming someone else’s.

Leveraging my extensive experience of over a decade in industrial sales, including a seven-year stint in the welding industry, I've observed the distinctive practices that catapult organizations to best-in-class status. A key component of these company’s success has been the power of blending Gratitude with Strategy—what I've coined as Grategy®. Implementing Grategy cultivates a work environment where excellence is not just pursued but flourished, and loyalty is deeply rooted.

To demystify this approach and revolutionize our understanding of workplace culture, I've developed the "Gears of Grategy." Far from being a mere set of tools, this innovative framework is designed to attract and retain top talent by nurturing a workplace culture anchored in positivity, recognition, and personal growth – and it all starts with YOU.

Integrating these gears into your air filtration business signifies a profound commitment to cultivating a culture that doesn't just attract good people but fosters their development and contribution towards your shared success. I'd like to hear how these gears have transformed your organizational culture and propelled your company forward. Without further ado, here they are.

The Six Gears of Grategy®

#Attitude: The Foundation: Above all else, your attitude matters. Beyond simple optimism, it's about embracing change as an opportunity, viewing innovation as essential, and committing to continuous improvement. Your perception and response to shifts in this dynamic sector greatly influences your professional growth and leadership potential.

The air filtration field's rapid evolution, marked by new technologies and regulations, demands an adaptable mindset. Seeing these changes as chances for growth, rather than obstacles, sets you apart and fuels your drive for innovative solutions. Resilience, fostered by a positive outlook, is key. It allows you to bounce back from setbacks and face challenges with confidence. Such an attitude is critical in a sector impacting public and environmental well-being. Embracing every situation as a learning opportunity prepares you to tackle both current and unforeseen challenges creatively.

Ultimately, adopting the right mindset is indispensable. Change, while intimidating, opens doors to growth and innovation. Your choice of attitude is totally up to you. Choose wisely.

#Appreciation: The Personal Touch of Gratitude: The second gear in the Grategy® model is appreciation, where you embrace gratitude on a personal level. My venture into gratitude began in 2009, a pivotal shift that has steered me through challenging times, including the recent pandemic. This journey has revealed that gratitude is more than positivity; it's a mindset that prompts you to find the good in every situation, backed by research showing its power to rewire your brain towards focusing on the positives, enhancing mental and physical health.

Making gratitude a daily practice helps you consistently recognizing the positives, even in adversity. This habit not only benefits you but also those around you, encouraging a deeper appreciation for the contributions of each member within your professional circle. Genuine acknowledgment of others' efforts enriches interactions, strengthening your leadership by demonstrating the importance of everyone’s role. This attitude of gratitude is not just beneficial—it's transformative, paving the way for a fulfilling professional and personal life.

#Access: Open Doors, Open Minds: This gear revolves around cultivating leadership that is not just approachable but genuinely accessible, fostering an environment where every member feels valued and their voice heard. It's about dismantling the traditional barriers between management and employees, thereby not merely opening doors, but also broadening minds.

Access transcends mere physical availability; it encompasses creating avenues for both personal and professional advancement. This involves implementing comprehensive training programs and providing resources that enable individuals to thrive, both within and beyond the confines of the workplace. When members feel supported in their growth, they are inspired to contribute their best.

The era of the one-size-fits-all approach to company culture is behind us. The contemporary workplace demands flexibility to accommodate the diverse needs and aspirations of its members. Leaders are encouraged to be not just physically present but actively engaged, seeking out feedback, and staying attuned to the workforce's evolving needs through proactive engagement methods like "stay" interviews. These discussions are gold mines of insight into the ambitions and concerns of employees, offering a proactive means to address potential issues and mitigate turnover risks.

By championing open communication and ensuring accessibility, you lay the foundations for trust and loyalty, which are crucial for retention. The Access gear guarantees that dialogue moves fluidly in both directions, cultivating a transparent and supportive culture that boosts engagement and propels the organization towards success.

#Applause: Recognizing and Celebrating Success: In the air filtration industry, recognizing achievements, both big and small, plays a pivotal role in driving progress and innovation. This is where the concept of #Applause becomes vital. Expressing gratitude, whether through verbal praise or a thoughtful handwritten note, not only creates memorable moments but also cements a culture of appreciation within your organization. Celebrating the milestones in the development of air purification technologies or acknowledging the dedication behind meeting stringent environmental standards fuels motivation and uplifts team spirit.

Personalization in recognition is key. Understanding what resonates with each member of your team, perhaps through preferences noted on an "All About Me" sheet, enhances the impact of your appreciation. Remember, there is no one-size-fits-all approach when it comes to recognizing the efforts of your people.

Moreover, recognition doesn't need to be extravagant. Simple gestures, such as a sincere "thank you," a personalized note, or a highlight in the internal newsletter, can significantly brighten someone's day. Encouraging peer recognition further strengthens team bonds, fostering a sense of unity and shared purpose.

In essence, the act of acknowledging and celebrating success is not just about boosting morale; it's about reinforcing the behaviors and innovations that lead to cleaner air and healthier environments. By integrating #Applause into your organizational culture, you highlight the importance of every achievement and contribution, big or small, in advancing the industry’s collective mission.

#ActsOfService: This fifth gear means extending the impact of your expertise in air filtration beyond the confines of daily tasks. It involves embedding corporate social responsibility and volunteerism into your core operations, significantly contributing to the health and well-being of communities and the environment. This initiative aligns perfectly with the deep-seated motivations that drew you to the air filtration industry: the desire to improve public health and protect the planet.

By participating in projects that enhance air quality, promote environmental sustainability, or educate the public about the benefits of clean air, you live out the values that attracted you to this field. Demonstrating to your team how their work transcends ordinary responsibilities to contribute to a grander mission fosters a profound sense of purpose and belonging.

This dedication to service transcends basic job functions and financial rewards. It's about showing the world the significant impact your industry can have. Through acts of service, you not only bolster team unity and attract like-minded professionals but also develop a brand that stands for meaningful change. For you, as part of NAFA, integrating acts of service into your ethos is crucial for inspiring continued innovation and leadership in air filtration, making every effort count towards a healthier, sustainable future.

#Accountability: Ensuring Alignment and Continuous Improvement: In the air filtration industry, #Accountability is crucial, serving as the cornerstone that ensures every effort contributes to your overarching goal: cleaner air and environmental protection. It's about more than just meeting benchmarks; it's a commitment to continuous improvement and adaptation. By implementing Key Performance Indicators (KPIs) specific to air quality enhancements and operational efficiencies, you measure the tangible impact of your work. However, accountability in this field goes beyond numbers; it's about being ready to evolve your strategies and technologies in response to new research and regulations.

This dedication to progress ensures that the pursuit of excellence is a never-ending journey. What may be effective today could be improved tomorrow, highlighting the necessity for ongoing adaptation and refinement. In the dynamic world of air filtration, accountability means embracing change and seeking ways to advance industry methods and outcomes continually.

By fostering a culture that values persistent growth, you encourage both leadership and team members to take ownership of their contributions to the mission. This approach doesn't signal an endpoint but rather propels the industry forward, ensuring that it remains at the forefront of environmental health and safety. Accountability, therefore, is not just a principle but a practice that reinvigorates your collective efforts, driving you towards innovation and excellence in every aspect of your work.

Why the Gears of Grategy® Matter

In the air filtration industry, the Gears of Grategy® are foundational to building a culture that not only attracts but also retains the brightest minds. At a time when professionals seek fulfillment beyond financial rewards, these gears offer a structured approach to fostering an environment that values, respects, and nurtures its talent. For NAFA members, embracing the Gears of Grategy® equips you to empower your teams, elevate performance levels, and forge a legacy of a positive workplace culture.

These gears are a testament to a commitment towards excellence. They envision a workplace where every individual feels valued, heard, and integral to the collective mission of improving air quality and environmental health. In the intricate and ever-evolving landscape of air filtration, adhering to the Gears of Grategy® shines a light on the path for leaders aspiring to steer their teams with compassion, integrity, and relentless dedication to excellence.

As we chart our course through the complexities of today's business environment, the Gears of Grategy® emerge as beacons for those determined to redefine standards of workplace excellence. They are a call to action for setting a new benchmark in the air filtration sector, emphasizing the importance of a workplace where innovation thrives, and every team member's contribution is recognized. If you're inspired to elevate your workplace using these principles, it's time to connect and embark on a transformative journey together.

Author: Lisa Ryan is the Chief Appreciation Strategist and Founder of Grategy where she is pioneering workplace culture transformation through the power of gratitude and strategy. To learn more, please visit LisaRyanSpeaks.com.

FIGURE 1: A visual representation illustrating:

First Image: Copper Creep Corrosion- Photographic and electron microscopic images depicting the degradation of copper plating on printed circuit boards as it transforms into copper sulfide. This progression extends across the boards, resulting in electrical shorts between nearby features and ultimately culminating in system failures ^{4, 6}.

Second Image: Silver Termination Corrosion- Electron microscopic depicting the silver terminations in surface-mounted components resulting in the degradation of silver metallization and the eventual occurrence of open circuits in components such as resistors ^{5, 6}.

Air Handling in Data Center

Data centers utilize air filtration systems that differ from conventional setups. They incorporate specialized units like the Computer Room Air Conditioner (CRAC) / Computer Room Air Handler (CRAH), housing filters along with fans, and cooling coils to ensure consistent room filtering. They are specifically designed to cool and regulate the temperature and humidity in the data center. Additionally, a standard Air Handling Unit manages incoming air from outside. Figure 2 illustrates the air handling system within a data center.

FIGURE 2: Illustration depicting the air handling system within a data center

Mitigation of Particulate Contamination

Effective particulate contamination control can be achieved with commonly available filters. ASHRAE recommends continuous room air filtering using MERV 8 filters, and suggests higher filtration levels like MERV 11 or MERV 13 for incoming air. Due to the energy-intensive nature of data centers, filters with low pressure drop and high dust holding capacity are preferred. Recently, Nanofiber filters, featuring thin layers on supportive substrates, have gained attention for their surface loading, which allows for effective dust accumulation. While in contrast, traditional filters experience depth loading over time, leading to blockages and increased pressure drops³.

Mitigation of Gaseous Contamination

To manage gaseous contamination, specialized filters called molecular filters are used. In data centers situated in areas with high gaseous contamination, it is recommended to deploy molecular filtration systems for both incoming and internal air. Table 1 outlines gaseous elements present in the environment, highlighting potential threats to data center components if they exceed specified control limits.

TABLE 1: Gaseous elements present in the environment and their impact on data center components when surpassing specified control limits⁶.

Molecular filters utilize adsorbent or chemisorbent media designed to capture gaseous contaminants. Depending on system design and contaminant characteristics, the media can be in the form of pellets, granules, or modules. Adsorbents, attracting molecules through forces like van der Waals forces, effectively capture low concentrations of non-reactive gases such as volatile organic compounds (VOCs), odors, and hydrocarbons. Activated carbon, with its extensive surface area, is a commonly used adsorbent capable of adsorbing a wide range of gases.

Chemisorbents chemically react with contaminants to form stable compounds, suitable for removing high concentrations of reactive gases like acids, bases, oxidants, and corrosives. Impregnated activated carbon, treated to enhance reactivity, is a frequently used chemisorbent in molecular filtration⁷. Some molecular filtration systems optimize performance by combining adsorbents and chemisorbents. For example, a system may use an adsorbent layer followed by a chemisorbent layer to eliminate both VOCs and acids from the air stream. Table 2 outlines various adsorbents widely used to address specific gaseous pollutants. Numerous ongoing studies are being reported aimed at developing new adsorbent materials with significant adsorption capacity.

When selecting a molecular filtration system for a specific application, several factors come into play, including the type and concentration of gaseous contaminants, the required airflow rate and pressure drop across the system, the desired removal efficiency and outlet concentration of contaminants, the operating temperature and humidity conditions, as well as the available space and budget for system installation and maintenance.

References:

Steve Greenberg, Evan Mills, and Bill Tschudi, Peter Rumsey, Bruce Myatt, Best Practices for Data Centers: Lessons Learned from Benchmarking 22 Data Centers, 2006, ACEEE Summer Study on Energy Efficiency in Buildings, 3, 76-87.
Henry C. Coles, Taewon Han, Phillip N. Price, Ashok J. Gadgil and William F. Tschudi, Air Corrosivity in U.S. Outdoor-Air-Cooled Data Centers is Similar to That in Conventional Data Centers, 2011, Lawrence Berkeley National Laboratory, 1-29.
ASHRAE, Gaseous and Particulate Contamination Guidelines For Data Centers, 2011
What is Creep Corrosion and How to Avoid or Mitigate It? (URL: https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z000000kIpsSAE)
Craig Hillman, Joelle Arnold, Seth Binfield, Jeremy Seppi, Silver And Sulfur: Case Studies, Physics, And Possible Solutions,2007, DfR Solutions, 1-13.
Chris Muller, What’s Creeping Around in Your Data Center?, 2010, ASHRAE Transactions, 1-15.
Jones, G., Rohrbach, R., Unger, P., Bause, D. et al., Wicking Fiber Chemisorption for Air Quality Improvement, 1997, SAE Technical Paper 970555,1-7.

Author: M.S.Giri Nandagopal, PhD, Product Development Engineer, Excelair Filters, Century Mechanical Systems Factory LLC

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