Indoor Air Resources

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Fight Colds and Flu with Better IAQ


By: Robert Martin, CAFS, Associate Category Manager, Kimberly-Clark Professional Filtration  |   10.16.14

Cold and flu season is right around the corner. And while providing building occupants with extra tissues and bottles of hand sanitizer goes a long way toward preventing the spread of germs, there is something else building owners and managers can do to keep their tenants healthier this winter: upgrade their HVAC air filtration system. 

How Colds and Flu Spread

Airborne infections like the common cold and influenza spread when bacteria or viruses travel on dust particles or small respiratory droplets that become aerosolized when an infected person sneezes or coughs. Healthy people can inhale the infectious droplets, or the droplets can land on their eyes, nose and mouth. People who inhale the airborne germs do not have to have face-to-face contact or be in the same room as the infected person. 

Filter the Air

Air filtration provides a prime defense for building occupants against airborne particles. 

HVAC system air filters remove respirable particles such as microorganisms, dust and allergens from the air. Many of these particles are three microns in size or smaller – a fraction of the size of a grain of sand. Lung-damaging dust, for example, can be as small as 0.5 microns, while some bacteria can be as small as 0.3 microns. These small, toxic particles are most likely to travel to the deepest part of the lungs, where they can cause a variety of respiratory problems. 

Capture Submicron Particles

When evaluating filters, it’s best to look for those that have high efficiency capturing the submicron particles that can cause health problems. These particles are called E1 (very fine particles in the 0.3 to 1.0 micron range) and E2 (fine particles in the 1.0 to 3.0 micron range) by the ASHRAE 52.2 test standard. 

High E1 and E2 efficiencies are critical for providing for good IAQ and helping building occupants avoid illness due to poor IAQ. However, many pleated air filters today (especially at commonly used MERV 8) have very low E1 and E2 efficiencies. In fact, under the ASHRAE 52.2 Standard, there is no minimum requirement threshold for E1 particle capture below a MERV 14 rating and no minimum requirement threshold for E2 particle capture below a MERV 9 rating. 

A Balanced Approach

Air filters with filtration media that combines a robust mechanical structure with the added benefit of an electret charge are able to be more efficient at particle capture – especially for submicron particles. 

Because a filter’s MERV rating does not necessarily indicate its ability to remove submicron E1 and E2 particles, it is possible for two similar filters of the same MERV rating (one using mechanical only media and the other using electret-treated media) to have different filtration efficiencies. For example, a MERV 8 electret-treated media filter could have better particle capture than a MERV 11 mechanical-only filter. Indeed, recent testing has shown MERV 8 filters using electret-treated media perform on average 20 percentage points higher in both E1 and E2 efficiency than mechanical filters on the market today. 

With the link between airborne particles and respiratory illness, one could deduce that filters with poor E1 and E2 efficiencies may be partially responsible for these illnesses, or at the very least, do little to help prevent them. 

A Healthier Cold & Flu Season

Each year in the U.S., there are millions of cases of the common cold – some estimates place this figure as high as 1+ billion -- and 5-20 percent of the U.S. population gets the flu. 

Help the occupants of your building to avoid becoming part of these groups or spreading their illness to others by upgrading your air filtration system for submicron particle capture. 


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