According to the Environmental Protection Agency, indoor air can be up to 100 times more polluted than outdoor air, and since we spend as much as 90 percent of our time indoors, the quality of the air in our homes and offices can significantly affect the quality of our lives and the quality of our health.
Heating, ventilation and air conditioning (HVAC) units can have an impact on indoor air quality. More than 70 percent of American households have central heating and air conditioning units, but nearly half of homeowners do not consistently change their air filters. Air filters are designed to remove polluting particles such as pollen, dust and mold from the air, but over time, those particles accumulate and eventually restrict air flow. As a result, a saturated air filter contributes to a decrease in HVAC efficiency and becomes its own source of air pollution. Regular air filter maintenance is one of the simplest, most inexpensive and most effective means to improve both the efficiency of an HVAC and the quality of indoor air.
The common blue or green spun fiberglass air filters are considered the “traditional” filters, but they may not be as efficient at cleaning the air as other filters.
When choosing and caring for air filters, there are several features to consider.
Generally, air filters are one inch to four inches in depth, and they are available in a variety of heights and widths. An air filter is usually labeled based on its nominal size, which is the size of the filter rounded up to the nearest inch. An air filter should fit snugly into its chamber and be equipped with a sturdy frame for proper air filtration. Consult your HVAC owner manual for manufacturer-recommended specifications.
There are several types of air filters that are commonly used for residential HVAC systems. Spun fiberglass air filters may be considered the “traditional” air filters. They are inexpensive, disposable and effective at capturing common air pollutants, but they should be replaced at least monthly for proper air filtration. Pleated air filters are a more efficient choice since they collect minute pollutants and require replacement about every three months. They are also disposable, but they are slightly more expensive than their spun fiberglass counterparts. Some filters feature an electrostatic charge to attract more polluting particles, and some filters feature an antimicrobial treatment to prevent pollutants from living on the filter where they are trapped. Washable air filters can be reused and require replacement only every few years, so they can reduce waste. However, they are not disposable and therefore must be cleaned regularly. Consult your HVAC owner manual for manufacturer-recommended specifications.
Many air filter manufacturers and retailers use their own systems to evaluate a filter’s ability to remove polluting particles from the air. But, the Minimum Efficiency Reporting Value (MERV) of the American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) is the only universal rating system for air filters. Residential air filters have MERV ratings of one to 12, depending on their abilities to capture miniscule particles. Most air filters remove large particles such as pollen, dust and lint quite adeptly, but filters with higher MERV ratings are more efficient and can capture microscopic mold spores, dust mite debris, pet dander, smoke, smog and even particles that carry viruses and odors. So, a higher MERV rating generally translates into cleaner air. Filters with higher MERV ratings also have to be replaced less often. ASHRAE recommends a filter with a MERV rating of at least six for most residences, but a filter with a nine to 12 MERV rating is considered the best choice, especially for households with people with allergies, asthma and other respiratory concerns. However, a filter with a MERV rating above 16 is not often recommended for residential filtration because it can actually restrict air flow, cause damage to HVAC systems and increase utility costs.
Some air filters, such as those made from spun fiberglass, have no pleating. Others are pleated. If you choose a pleated version, choose a filter with more pleats per foot, which has more filter media for cleaner, more efficient air flow.
Remember: every disposable air filter needs to be replaced at least every one to three months to maintain proper HVAC operation and to improve air quality. Washable air filters must be cleaned regularly, too. A filter may require replacement or maintenance more often if a member of the household smokes, if a member of the household suffers from respiratory concerns, if the home is located in a dusty or polluted area, or if the filter becomes saturated with polluting particles, especially at certain times of the year such as pollen season.