FILTER OUT IAQ PROBLEMS
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FILTER OUT IAQ PROBLEMS |
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Learn these three basic aspects of filtration to develop a practical, step-by-step approach to better indoor air quality.
Just a few years ago, the topic of indoor air quality (IAQ) was virtually unknown outside of professional journals and industry trade publications. Now, it's well-known that the quality of indoor air affects everyone, and IAQ stories are becoming commonplace in the popular media.
As IAQ horror stories surface from buildings across the country, building owners are asking contractors if there are any practical, short-term, and - more importantly - relatively inexpensive steps that can be taken to improve IAQ. Thankfully, there are.
IAQ is a complex topic covering a number of professional disciplines. It's complicated by the specific - and often unique - needs of various indoor environments. More complexity is added to the challenge of achieving good IAQ by the fact that there is no single solution (or source) should a problem arise, and there are no unified recommendations addressing it from professional and trade organizations.
So what should a professional who is managing the operation and maintenance of HVAC systems do? Through extensive research and our experience as the world's largest supplier of air filtration products, we believe there are three key elements that can be addressed to help eliminate the HVAC system as a potential source for IAQ issues. Put simply, these elements are:
In this case, the it refers to fine particulate. There are a number of good papers discussing fine particulate and its effect on health. One recent study quantified the effect of particulate on general mortality: "Fine particles (those with aerodynamic diameters equal to or less than 2.5 (m) are the largest health concern because they can be breathed most deeply into the lung...In this study, sulfate and fine particulate air pollution were associated with a difference of approximately 15 to 17% between mortality risks in the most polluted cities and those in the least polluted cities." (Source: Pope C.A., Thun M.J., et al. Am J Respir Crit Care Med: Vol. 151;669-674).
As you're probably aware, the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE) is revising its Standard 62-1989R, Ventilation for Acceptable Indoor Air Quality. From the public drafts, it appears this document will combine recommendations on both ventilation and filtration.
This is important since ASHRAE has written the standard in code language, revealing its strong stance on the benefits of combining ventilation and filtration. In fact, the current draft includes recommendations on minimum filtration levels under specific circumstances.
The recommended minimum filtration level expressed in the new Standard 52.2R is a 25 to 30% efficient pleated filter, (as rated by ASHRAE Standard 52.1, Atmospheric Dust Spot Method). The systems addressed by this ASHRAE standard are defined as "Mechanical ventilation systems with fin tube heating coils; supply ductwork exceeding 3m (10 ft.) in length; humidifier, evaporative cooler or cooling coils."
But what should HVAC professionals do to improve IAQ regardless of the recommendations eventually set forth by Standard 62-1989R?
The best strategy is to point their customers to the highest filtration level that makes technical and economic sense. If the customer's only option, without costly equipment upgrades, is to move up from a fiberglass throw-away filter to a cotton polyester pleated filter, then that's what they should do.
While most commercial and industrial air handlers can effectively use a 90 to 95% efficient bag or rigid cell filter, IAQ issues extend to more than just high levels of filtration. Maintenance of the HVAC system and the system's air filters is just as important as the efficiency of the filters.
Regular preventive maintenance programs are often overlooked in the discussion of IAQ. This can be a critical oversight, as such programs demonstrate the minimal level of care and constitute the due diligence of the facility manager or building owner.
Given the current regulatory climate, it appears unlikely that the proposed rule on IAQ by the Occupational Safety and Health Administration (OSHA) will pass in the foreseeable future. A more likely scenario would be the inclusion of the revised version of ASHRAE Standard 62-1989R into local or state regulations, either by reference or adaptation of the standard's code language.
Regardless of its status, the proposed rule has served to add a standard of care for the HVAC community to the public record. One of the cornerstones of the rule is the documentation of regular preventive maintenance undertaken by the building owner or manager. In most well-run HVAC operations, this documentation is already in place. Making sure your building owner clients keep complete records in this area helps minimize their potential for future litigation based on IAQ issues associated with the HVAC system.
In this case, it refers to microbial growth on the air filtration media. According to a recent study, dust accounts for roughly 25% of the contaminants resulting in IAQ problems. So, until the advent of the use of antimicrobials in the air filtration industry, manufacturers only concerned themselves with one-fourth of the airborne contaminants that could potentially cause IAQ problems.
However, whenever high efficiency air filtration products are used, the possibility that the air filtration media will also trap microbes increases. The media, and the particulate it has trapped, then can become the source of amplified microbial growth. The use of a broad-spectrum antimicrobial treatment will minimize the potential for the filter media to act as the source, or incubator, of microbial growth.
A recent study sponsored by ASHRAE summarized the specifics of the microbes affecting IAQ. In its introduction, the study succinctly defines this issue..."A current challenge in the HVAC field is the control of microbial aerosols. Microbial aerosols contain organisms such as bacteria, fungi, algae, protozoa, pollen, and viruses. Many of these particles cause allergic reactions and/or are the causative agents of various infectious diseases. Good indoor air quality constitutes the control of both nuisance dust and microbial particles."
Other studies also cite the adverse effect of microbial growth on IAQ. The findings of these studies indicate that fungi and bacterial account for nearly twice the number of causes of IAQ problems as dust.
What does this mean in the indoor environment? It means an air filter is a point source of microbial growth at the beginning of an HVAC system. When potentially harmful microbes grow on a filter media, their size and the fact that they can remain airborne and viable means they can be broadcast throughout the areas served by an air handling unit.
Many HVAC systems use 100% outside air to help limit the building's exposure to microbial growth. However, the use of 100% outside air doesn't eliminate the need for control of microbial growth on the air filter media, or diminish the potential adverse effect of that growth on occupants in the facility.
The moisture level within an indoor environment is a key variable determining the potential for microbial growth on indoor air surfaces, including air filter media. The ability (or, more accurately, the inability) to control moisture is the critical issue calling for the use of antimicrobials on indoor surfaces.
If HVAC management could completely and constantly control moisture to an acceptable level, the need for antimicrobial treatment would be eliminated. But in reality, most buildings are not in total and constant control of the moisture level - weather, power outages, energy control efforts, and so on make that impossible without expensive back-up systems that just don't make economic sense. Therefore, the use of antimicrobial treated surfaces is an economical, proactive step in protecting building occupants from the potential for microbial growth emanating from the air filter media.
With all of the promotion of antimicrobial treatments by a number of manufacturers for various indoor surfaces (carpeting, paint and coatings, ceiling tiles, fabrics, etc.), including air filtration media, how can contractors be assured that the chemicals they're using are safe for their intended use? Ask the manufacturer of the final product to provide the manufacturer's safety data sheet (MSDS) for the active chemical used as an antimicrobial treatment. The manufacturer should also provide the stamped EPA technical data sheet documenting the fact that the product has been tested by an independent lab and is safe for its intended end use.
For air filtration products, the critical issue is off-gassing of the antimicrobial. The antimicrobial manufacturers have to demonstrate to the EPA that the antimicrobial doesn't enter the air stream at levels measurable by analytical equipment.
Every air filter, no matter how efficient, is also inefficient to a certain extent. No filter traps every particle or microbe. Elimination of unfiltered point sources within the HVAC system has the same benefits to the indoor environment as the use of antimicrobials in air filtration media. The only way to ensure these point sources are controlled is to keep them clean and free of microbial growth.
There are many potential areas in the HVAC system that can act as reservoirs for microbial growth. Cooling coils are one of the most likely areas to trap microbes and dirt. Coil cleaning and sanitizing products with biocidal characteristics can help control the microbial growth on these surfaces. Some of the considerations in choosing one of these products are:
Since all surfaces in an indoor environment can contribute to poor IAQ, it's important to take your efforts beyond the air filters and cooling coils. While a comprehensive preventive maintenance program is clearly the cornerstone of better IAQ, the implementation of antimicrobial treated indoor surfaces such as carpet and carpet tiles is an insurance policy that these surfaces do not contribute to further amplification of microbial growth. Of course, the sheer square footage of the potentially affected area makes the investigation and the control of indoor surfaces a daunting task.
In conclusion, our research into indoor air quality has demonstrated that there's no one single product, solution or "fix" that yields better IAQ. While some of the issues associated with IAQ are quite complex, the most effective solutions and improvements are based on good common sense and the effective control of fine particulate and point sources of microbial growth within the indoor environment.
Thomas Capes is a market development manager for AAF International, the manufacturer and marketer of AmericanAirFilter products, Louisville, KY. He points out that the many complicated aspects of IAQ make this article, by necessity, a brief overview. Readers interested in the studies that were the basis for this article, and which discuss the specifics of air filtration and IAQ in more detail, may contact Tom at 502/637-0352, or call the AAF Answer Center toll free at 888/223-2003.