Resources - Air Filters Buyer’s Guide

The Indoor Air Quality (IAQ) at your facility can have a profound impact on employee health. According to the United States’ Environmental Protection Agency, indoor air quality is routinely 2-5 times worse than the air quality outside. In extreme circumstances, IAQ can be up to 100 times more polluted, and when you combine that fact with the realization that approximately 90% of our time is spent indoors, IAQ is something that shouldn’t be ignored by facility executives.

At the center of good indoor air quality is proper air filtration.

Buildings generate pollutants that range from the air drawn in for the HVAC system to gaseous buildup and more. Air filtration acts as a first line of defense for the occupants of the building and for the HVAC system. Swirling about in the air we breathe is a lengthy list of undesirables:

- Lint, dust, & pollen
- Dust mite debris, mold spores, & pet dander
- Smoke, smog, & bacteria

In addition to the health of employees, filtration impacts the health of the overall HVAC system -- a significant investment for your business. Air filters reduce the amount of dust and other particles reaching the wet coils used for cooling, which then prevents those contaminants from becoming food for mold that can accumulate on the coils and in the ducts. In addition, clogged filters can slow the airflow, causing the system to work harder, or produce an uneven air flow which also impacts overall performance of the system.

Therefore, a building’s HVAC air filtration system provides tangible ways to improve IAQ and energy efficiency - two critical forces bearing down on the bottom line. In fact, the right filter media strategy can even help buildings become “greener” and meet various green building rating system criteria.

The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) has developed two HVAC industry standards that characterize air filtration:

ASHRAE 52.1-1992 - This standard was designed to measure a filter’s pressure drop and dust holding capacity. The higher the pressure drop, the lower the air flow to the HVAC unit, which will result in more energy required to operate the system. Additionally, a filter with higher dust holding capacity will result in a filter that lasts longer.

ASHRAE 52.2-1999 - This standard measures the fractional particle size efficiency of an HVAC filter.

The particle size efficiency of a filter can be measured in three ways:

MERV Rating (Minimum Efficiency Reporting Value) - The only rating system created and regulated through the standards set by ASHRAE. MERV rates the capacity of a filter to capture and hold dust particles. The MERV rating system is the primary rating system used in the industry in the United States and internationally.

MPR (Micro-Particle Performance Rating) - An MPR rating applies to a filter’s ability to capture airborne particles smaller in size than 1 micron. The MPR rating system was created by 3M and is used solely with 3M brands, including Filtrete.

FPR (Filter Performance Rating) - An FPR rating measures a filter’s capacity to capture large and small particles, as well as the filter’s expected lifetime. The FPR rating system was created by The Home Depot and is used solely on The Home Depot brands, including Honeywell.

Though a direct comparison of these three rating systems is difficult because the metrics used are different, cross-referencing and research suggests the following: