Air Filters: What About All These Different MERV Ratings?

The air in your San Antonio home contains particulate pollutants like mold spores, bacteria, viruses and dust mite debris. In fact, the Environmental Protection Agency says indoor air can be more hazardous to your health than the air outside. The air filter in your HVAC system traps many of these particles and can improve your indoor-air quality.

The effectiveness of air filters is measured on a minimum efficiency reporting value, or MERV, scale, which ranges from 1 to 20. MERV ratings of 13 and higher are designed for hospitals, certain manufacturing operations and air purifiers/cleaners. They aren’t suitable for most standard air conditioners and furnaces.

Depending on your air-quality needs and such factors as the amount of dust that enters your home and whether you have pets, you can choose a low-, medium- or high-quality air filter.

  • Low-quality air filters range from 1 to 4 on the MERV scale. These inexpensive filters are made of fiberglass and aren’t pleated, which means there’s less area for trapping particles. While this type of filter will keep your HVAC system’s components clean, it won’t do much to improve your air quality, because it only traps particles larger than 10 microns, such as pollen, carpet fibers and dust mites.
  • Medium-quality pleated air filters range from 5 to 8 on the MERV scale. These are the most commonly used filters and trap particles down to 3 microns, including mold spores and hair spray.
  • High-quality air filters range from 9 to 12 on the MERV scale. These filters are ideal for those who suffer from allergies, asthma and other respiratory illnesses. They trap particles as small as one micron, including certain bacteria and lead dust.

Before upgrading your current filter type, check the specs of your HVAC system to determine the best filter to use. Also talk with your HVAC-system professional. A 1-inch filter–which you find in most home-improvement stores–may be too restrictive for your furnace or air conditioner, and your HVAC professional might recommend a 4- or 5-inch filter.

For more expert advice on choosing and using air filters, contact Beyer Boys. We keep San Antonio-area residents comfortable year round.

Our goal is to help educate our customers in the greater San Antonio, Texas area about energy and home comfort issues (specific to HVAC systems).