Indoor air pollution is a serious problem especially for people with allergies. In fact, most of the time, the air indoors is more polluted than the air outside, due to dust, dust mites, bacteria, mold, and viruses. Studies indicate that the pollution is 2 to 5 times higher than with outdoor air. While some people may not believe this because the pollens outside can trigger their allergies, the truth is in the evidence. There are much higher quantities of various air pollutants in samples of indoor air than outdoor.
With these indoor air pollution concerns, it is no wonder why many people turn to their HVAC system to help filter the air that it circulates. Otherwise, it just moves the irritants from room to room. HVAC filters are not all efficient at removing significant amounts of allergens and irritants from the air. It is important to select a filter that can clean out even the smaller particles.
Filters are measured by minimum efficiency recording value (MERVs) ranging from 1 to 20 with 20 filtering the highest level of pollutants from the air. Flat panel filters only rank from 1 to 4 on the MERV scale and are really only filtering particles large enough to protect the furnace, not to protect human beings.
Medium efficiency filters are pleated and, with the increased surface area, can pick up more particles, reaching a MERV rating of 5 to 13. High efficiency filters are made of thicker materials and can pick up enough particles to reach a rating of 14 to 16.
Finally, HEPA filters rank from 17 to 20, removing the maximum amount of particles from the air.
The only concern with the higher level filters, other than the greater expense, is that they require more energy as the fan has to push harder to pass air through the thicker materials. And replacing filters on schedule is important for maintaining a functioning HVAC system and clean air. But for those concerned with having clean indoor air, the benefits outweigh the costs.