Are you using the best type of air filter in your furnace or air handler for optimal indoor air quality? The Environmental Protection Agency lists indoor air pollution as one of the top five environmental health risks and lists air filters as a method of improving air quality. There are several types of air filters, so which type is best for you?
The pollutants you should be concerned about are respirable particles, those less than 2.5 micrometers in diameter. These are a health risk because when inhaled they can lodge in your lungs. Respirable particles include viruses, bacteria, mold, and pollen spores, among others.
Check any filter’s MERV (Minimum Efficiency Reporting Value) rating. This number, on a scale from 1 to 20, indicates the percentage of particles the filter traps. The higher the number, the better. Aim for at least an eight, but 11 or 12 is superior for residential use, trapping up to95% of particles. MERV values above 12 are generally for hospitals and other sterile environments.
When it comes to the filter itself, there are many choices.
- Flat or panel filters are the least expensive, and the least effective. They generally have a MERV rating of 1 to 4, trapping larger dust particles but not respirable particles.
- Electrostatic air filters have been statically charged to draw larger particles, such as dirt and dust, to them. However, they only block about 20% of particulates. Some can be washed and reused; look for one with a lifetime guarantee.
- Pleated filters are the most popular for residential use. Pleating increases the surface area and therefore the percentage of particles trapped. They have a MERV of between five and 13. This is enough for families without allergies or respiratory issues.
- Higher efficiency pleated filters, with a MERV of 14 to 16, are sometimes incorrectly called HEPA or HEPA-type filters. True HEPA (High Efficiency Particulate Air) filters have MERV values of 17 to 20, but are rarely installed in residences. If you have allergies, the good news is that filters with a MERV between 7 and 13 are almost as effective as true HEPA filters.
- Charcoal, or activated carbon, air filters are for removing odors such as pet odor, garbage, and cigarette smoke. They can be pleated or unpleated; the best pleated ones have a MERV of around eight but are not as effective against particulates as standard pleated filters.
Whatever air filter you choose should be changed or cleaned monthly, especially during months of peak usage. Doing so increases the efficiency of both the filter and the furnace or air handler. There are several types of air filters and each has its own advantages and disadvantages; it’s up to you to decide which is best in your situation.