Air filtration is an important part of your home’s ventilation system. Without an air filter in place, dust and other airborne particles would be distributed throughout your ductwork. This could aggravate allergies, build up on your vents to reduce airflow and possibly even create bigger problems over time.

This doesn’t mean that you can just grab any air filter and slap it in place, of course. Choosing the right air filter for your home is important if you want to get the most life out of your heating and cooling system. Stop for a moment and think about your HVAC system; do you really know what sort of air filter you need to keep things running in top condition? If you don’t, here’s what you need to know.

Where Is My Air Filter?

The first thing that you need to know about your air filter is exactly where in your house it’s located. This may seem kind of obvious, but some air filters are difficult to find. While the most common air filter location is behind a grate on one of the walls, some of these grates are in odd locations or are designed to somewhat blend in with the look of the surrounding wall. Filters may also be placed in the air handler unit (AHU) or rooftop unit (RTU). Buildings with split ventilation systems may even have multiple intakes that each have their own air filter. Depending on how your system is designed, it may take a bit of hunting to locate your filter.

Choosing an Air Filter

Once you’ve located your filter, it’s important that you choose the right one for your needs. Part of this involves finding the right size filter; different HVAC units are designed for different filters, and if you get one that doesn’t fit then you’re going to have trouble getting it (or keeping it) in place. Measure the dimensions of the area where the filter is mounted or look at the old filter and find the dimensions listed on it. Choosing an air filter is about more than just finding the right size, however; one other big consideration is the MERV rating (which stands for Minimum Efficiency Reporting Value.)
 

The MERV is a number that tells how good of a filter you’re buying. A low MERV of around 6 provides you with 35 to 50 percent efficiency at capturing large particles like dust, mold and pet dander. A MERV of 8 increases this to over 70 percent efficiency, capturing those particles as well as slightly smaller particles like pollen and dust mites. A MERV of 11 captures large particles with a greater than 85 percent efficiency, as well as medium particles like those found in auto exhaust with 65 to 80 percent efficiency. You can even go higher than that, with a MERV of 13 capturing large and medium particles with over 90 percent efficiency and small particles like smoke, bacteria and even odors with up to 75 percent efficiency.
 

There are other options available as well, such as HEPA filters (which you might hear referred to as high-efficiency particulate arrestance filters or high-efficiency particular air filters) that have an even higher standard of particle removal. HEPA filters must remove either 99.95 percent (in Europe) or 99.97 percent (in the United States) of all particles of size “small” or larger. Depending on the filter, this translates to a MERV value of around 17 to 20.

Air Filter Maintenance

There’s more to keeping your system running well than just installing a filter, of course. Most air filters should be changed monthly, though some may have different recommended use periods that should be listed on the packaging. Periodic cleaning of grates and vents may also be required to keep the filters clean and the system running efficiently. Failing to change your filters can reduce airflow and system efficiency, and over time, it can even reduce the life of your unit.