How well your central heating and cooling system cleans the air largely depends on the quality of your air conditioner filters.
Filters are rated from 1 to 16 on the Minimum Efficiency Reporting Value scale. The MERV scale is based on the percentage of particles, from 0.3 to 10 microns in size, that the filter catches. The higher the MERV number, the better it filters the air.
The Microparticle Performance Rating measures very small particles between 0.3 and 1 microns. Ratings on the MPR scale range from 0-2200. The higher the number, the smaller the particles that a filter removes.
Mold spores and pollen are usually in the 10-30 micron range; bacteria, 2-3 micron; and tobacco smoke, 0.5 micron.
Understanding the MERV Scale
Here are some guidelines to consider when choosing air conditioner filters:
- MERV 1-4 Air Filters: These inexpensive fiberglass mesh filters only remove particles over 10 microns in size. They do little to improve the indoor air quality in your home.
- 5-8 Air Filters: These medium-quality pleated air filters can remove particles down to 3.0 microns in size.
- 9-12 Air Filters: These high-quality air filters can remove particles down to 1.0 microns in size.
- 13-16 Air Filters: These are the highest-quality, standard filters. They can remove particles down to 0.3 microns.
- 17-20 Air Filters: These filters, also known as HEPA (High Energy Particulate Air) air filters surpass the standard MERV rating by removing 99.97% of airborne particles 0.3 micron and larger. While often used in hospitals, they cause too much air resistance to be installed in a standard HVAC system without making modifications.
Other Ways to Reduce Allergens
In addition to choosing quality air conditioner filters and changing them regularly, you can do other things to help clear the air in your home.
Here are some examples:
- Limit or remove carpets and rugs.
- Keep pets outdoors.
- Reduce Volatile Organic Compounds in your home.
- Use a quality vacuum cleaner equipped with a HEPA filter.
- Install a room air purifier equipped with a HEPA filter.
Further, certain houseplants can improve air quality. These include philodendron, peace lily, dracaena and snake plant.
More on Air Conditioner Filters and Indoor Air Quality
- Changing the Air Filter in Your Home (video)
- Choosing Air Filters for Your Home (video)
- How to Find the Air Filter for the HVAC System in Your Home (article)
- Guide to Air Cleaners in the Home (EPA)