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Air filtration:

Guidelines and standards for using air filters

lan C. Veeck of the National Air Filtration Association takes us through the various regulations and standards that affect the usage of air filters in the USA.

Many industries are regulated with Congressional Acts and laws that safeguard the health and welfare of workers and the general public. The food we eat, prompted by the book, The Jungle, by Upton Sinclair, led to the Meat Inspection Act, the water we drink, known to cause several diseases identified as waterborne, is inspected and tested constantly to meet Government standards, and the outdoor air we breathe, prompted by a book by Rachel Carson called Silent Spring, led to the formation of the Environmental Protection Agency and the consolidation of research, testing, monitoring, standard-setting and enforcement of outdoor contaminants by the Government.

An effort mounted in the early 1980’s by EPA to regulate the indoor environment became a difficult effort and was basically abandoned. While several specific industries such as dry cleaning establishments and painting facilities, and some public buildings have indoor air laws and regulations, there is no broad overall law regulating most typical indoor environments. (One exception here is environmental tobacco smoke (ETS) which is an example of state and city laws being passed to prohibit smoking not only in public places, but in private establishments such as restaurants and other facilities). Private organisations have stepped in to recommend guidelines and standards for indoor environments with the American Society of Heating, Refrigerating and Air Conditioning Engineers, (ASHRAE) being one of the more prominent.

ASHRAE developed a method of test for air filters called ANSI/ASHRAE 52.2-1999. The method reports air filter efficiency by particle sise – from 0.3 micrometers to 10 micrometers – with a single number called a minimum

efficiency reporting value (MERV). The MERV has been incorporated into other organisational guidelines and standards.

Let’s take a look at some standards and guidelines and some common sense “best practice” recommendations being used in many indoor environments that should give

all of us a good reason to utilise the best possible air filtration in our facility. We begin this with the understanding that we spend about 90% of our entire lives indoors.

Residential

We spend about half of our life in our home and cooking is one of the biggest sources

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As we spend so much of our life indoors, we all have a good reason to utilise the best air filtration in our facility.

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of contaminants in most homes. With the explosion in the cooking market fueled by television shows, people are doing much more cooking in the home than pre-2000 levels. Most of these cooking aficionados use gas appliances which provide molecular contaminants as well as particles.

ANSI/ASHRAE Standard 62.2 is a residential ventilation standard that incorporates a recommended MERV of, 6 or better. MERV filters capture greater than 50% of particles in the 3.0 to 10.0 micrometer range. MERV 6 is a big improvement over MERV 1-4 (older style fiberglass filters) that were designed to remove lint and large dust particles. This MERV 6 or better criteria comes with another caveat. The Standard states, “The filter shall be selected and sised to operate at a clean pressure drop no greater than 0.1 in.w.c. Most residential systems only allow about 0.5 inches of external static pressure

allowing about 0.1 inch for the filter. It doesn’t take a rocket scientist to understand that a higher MERV filter in most instances comes with a higher pressure drop and MERV 6+ filters equates to a lower velocity of air from the system, longer run times to satisfy a thermostat, premature aging of HVAC components and usually a larger electric bill.

Best practice for better contaminant removal is to retrofit the system with a filter designed to provide higher efficiency and a lower pressure at residential HVAC pressure drop. Another option is to purchase a room air cleaner that conforms to ANSI/AHAM AC-1-2006. This Standard method of test for air cleaners is recognised as the best method of determining which units provide the best clean air delivery rate (CADR). Many media and electronic air cleaners are available from HVAC and NAFA distributors.

Commercial

ANSI/ASHRAE 62.2-2004 provides for a MERV of, “…not less than 6…” This MERV is the same as the residential standard and while seeming low, does at least establish a baseline. Most buildings require higher levels to achieve good air cleaning including many schools that now utilise MERV 15, and many commercial buildings following LEED recommendations of MERV 8 and MERV 13.

Hospitals

The American Institute of Architects (AIA) Academy has authority in the construction of hospitals and has published, “Guidelines for Design and Construction of Hospital and Health Care Facilities.” This publication recommends HEPA filtration for critical areas in the hospital such as surgery, and ICU, special filtration and ventilation requirements for isolation rooms, MERV 14 for less critical

Table

Standard 52.2

Minimum Efficiency

Reporting Value (MERV)

Composite Average Particle Sise Efficiency,

% in Size Range µmAverage ASHRAE Arrestance, %, by Standard

52.1 Method

Minimum Final Resistance

Range 1(0.3 – 1.0)

Range 2(1.0 – 3.0)

Range 3(3.0 – 10.0) PA Inches of Water

1 n/a n/a E3 < 20 Aavg < 65 75 .3

2 n/a n/a E3 < 20 65 ≤ Aavg < 70 75 .3

3 n/a n/a E3 < 20 70 ≤ Aavg < 75 75 .3

4 n/a n/a E3 < 20 75 ≤ Aavg 75 .3

5 n/a n/a 20 ≤ E3 < 35 n/a 150 .6

6 n/a n/a 35 ≤ E3 < 50 n/a 150 .6

7 n/a n/a 50 ≤ E3 < 70 n/a 150 .6

8 n/a n/a 70 ≤ E3 n/a 150 .6

9 n/a E2 < 50 85 ≤ E3 n/a 250 1.0

10 n/a 50 ≤ E2 < 65 85 ≤ E3 n/a 250 1.0

11 n/a 65 ≤ E2 < 80 85 ≤ E3 n/a 250 1.0

12 n/a 80 ≤ E2 90 ≤ E3 n/a 250 1.0

13 E1 < 75 90 ≤ E2 90 ≤ E3 n/a 350 1.4

14 75 ≤ E1 < 85 90 ≤ E2 90 ≤ E3 n/a 350 1.4

15 85 ≤ E1 < 95 90v ≤ E2 90 ≤ E3 n/a 350 1.4

16 95 ≤ E1 95 ≤ E2 95 ≤ E3 n/a 350 1.4

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areas and MERV 6 for non-critical areas. Their recommendations are echoed in ASHRAE’s publication, “HVAC Design Manual for Hospitals and Clinics.”

Because of the influx of large numbers of people into the hospital environment, waiting rooms, emergency rooms and visitors, we believe there is a tremendous opportunity for bacteria, fungi and viruses and other contaminants and communicable diseases to be transported from the outside on clothing and through the air. Hospitals need to upgrade filtration requirements even for “non-critical” areas of the facility in order to assure that they have the cleanest air possible indoors. In addition, many one-day surgeries being performed in facilities other than a hospital

need to upgrade their filtration to operating room guidelines.

Because there are so many different applications in the commercial/institutional area for occupants, suffice it to say that there are some unique applications that use filtration for an economic reason;

Libraries, archives and museums (LAM)

Let’s not forget that items other than people can “suffer” from poor indoor air. And haven’t you wondered what turned the paper in that old high school yearbook yellow? Yes, it’s our contaminant friends from the environment. And while your yearbook looks bad to you,

look at the loss of valuable painting by the great masters like Da Vinci and Michelangelo, written documents like the US Constitution, and artefacts manufactured in the early part of the history of humanity. How do we preserve these for generations to come?

Most of the contaminants, both particles and gas-phase called molecular, can be removed from the environment through good air filtration. In the case of libraries, archives and museums, a three-filter bank approach that removes both large and small particles combined with an adsorbent media such as carbon or potassium permanganate provides the removal capacity to protect and preserve priceless items for hundreds of years. NAFA’s Libraries, Archives and Museums Guideline describes in detail the best practice way to remove contaminants.

Firing ranges

Because of the amount of lead and other contaminants involved in the discharge of firearms, firing ranges must utilise HEPA filtration, molecular filtration and correct amounts of dilution ventilation to achieve safe air quality in the facility. NAFA’s Firing Range Guideline is an excellent source of information for this purpose.

Industrial

Most all industrial activities come with a laws and regulations from OSHA or NIOSH to assure that the process does not harm the health of the worker. A good example of this would be the OSHA laws regulating metal working fluids, welding smoke and dust separation equipment used in the woodworking industry. Many of the laws and regulations are found online at www.epa.gov.

Summary

There are many laws and regulations regarding environments that pose a potential hazard to people. Standards and guidelines for cleaning the indoor environment are every bit as important as assuring that the outdoor environment is clean. While EPA is charged with the latter, NAFA, ASHARE and other organisations in the HVAC industry are actively involved to recommend best practice application to the indoor environment. Looking at the way we clean more critical applications can give us a good idea of what we should be doing in a typical environment to better clean the air. •Contact:Alan C. Veeck is Executive Director of the National Air Filtration Association and a Certified Air Filter Specialist and NAFA Certified Technician. He has been working in the air filter industry since 1985 and has been actively involved in all phases of contaminant control and air cleaning. He can be reached at www.nafahq.org

Most buildings require higher levels to achieve good air cleaning – many commercial buildings follow LEED recommendations of MERV 8 and MERV 13.

The appropriate use of air filtration assists in preserving literary masterpieces for generations to come.

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