The recent flu season was the worst in nearly a decade. Families, businesses, schools — just about everyone — felt the impact of either getting sick or trying to avoid it. While it’s always best to heed the specific advice of healthcare professionals during cold and flu season, there’s one way to help keep germs like the influenza virus from spreading as readily throughout buildings: a robust air filtration system to improve indoor air quality (IAQ).
Removing Dangerous Particles from the Air
Most of the respirable dust and particles people breathe into their lungs is approximately 7 microns or smaller – a fraction of the size of a grain of sand. The smallest, most toxic particles (2.5 microns in diameter or less) are most likely to travel to the deepest part of the lungs, where they can cause a variety of respiratory and other health problems. But it’s really the submicron-sized particles that are of most concern; airborne bacteria can be as small as 0.3 microns.
A filter’s Minimum Efficiency Reporting Value (MERV) provides important information about its efficiency in removing dangerous submicron particles from the air. Evaluation of the full ASHRAE 52.2 test report (specifically the Fractional Particle Size vs. Particle Diameter Curve) will provide efficiency data over three particle size ranges: E1 (very fine particles in the 0.3 to 1.0 micron range), E2 (fine particles in the 1.0 to 3.0 micron range), and E2 (coarse particles in the 3.0 to 10.0 micron range). High E1 and E2 efficiencies are critical for providing for good IAQ and helping building occupants avoid illness due to poor IAQ.
Some pleated filters today (especially at commonly used MERV 8) have very low E1 and E2 efficiencies. In fact, under the ASHRAE 52.2 Standard, there was no minimum requirement for E1 particulate capture below a MERV 14 and no minimum requirement for E2 particle capture below a MERV 9 until recently. It is therefore possible to have a MERV 8 filter with better E1 particle capture than a MERV 11 filter, depending on the filter media used.
A Balanced Approach to Air Filtration
For filters with high initial and high sustained filtration efficiency over their lifecycle, specify filter media that has a good balance of mechanical efficiency and electret efficiency (via an electrostatic charge).
The electrostatic effects created in an electret-charged media are particularly useful increasing the capture of submicron particles, thus filters with electret-charged media often provide better E1 and E2 performance than is required by their MERV rating. In addition, recent testing showed MERV 8 filters using electret-charged media performing on average 20 percentage points higher in E1 and E2 efficiency than mechanical filters on the market today.
Better IAQ for Better Health
Infectious particles can stay airborne for hours and be transported over long distances. A robust air filtration system may help reduce the spread of infectious particles like the influenza virus. In fact, using air filters that capture particles 2.5 microns or smaller can lead to substantial health benefits.
The filter supply chain would be well-served to better understand the IAQ and health benefits of air filtration to help improve the health of building occupants during cold and flu season.