Air quality is a big concern, but many people often forget to regularly do one thing that will help them breathe easier in their homes.

Changing air filters, also called furnace filters, can make a difference in the air quality circulating in people’s homes.

Air filters are needed to keep the components in a home’s heating and cooling system clean.

“Once a filter is real dirty, it will begin to restrict air flow,” says Michael Hollander, general manager of The Joseph Co., a Fresno, Calif., business that services heating and air-conditioning systems, cleans air ducts, and tests and removes mold. “When that happens, you are asking (the heating and air-conditioning) unit to work harder.”

But filters also clean and clear the air by trapping dust, dirt, animal dander and other particles.

Most filters for homes are 1 inch thick. Inexpensive filters are made of fiberglass or polyester and should be changed monthly. These filters usually cost less than $1 each at home-improvement, hardware and department stores.

Washable or reusable filters usually have an initial high cost but can be used for years before they need to be replaced. They should be washed monthly. The Home Depot sells washable filters for $19.97 each.

Other filters, made with cotton or polyester material, are pleated or flat and should be changed every two to three months. At The Home Depot, these filters start at $3.97 each. “More and more, people are buying the pleated ones,” Hollander says. “They have more filtering surface, are denser and trap more material.”

There also are electrostatic filters in which the fibers are electrostatically charged, drawing smaller particles to the filter. These filters should be changed every two to three months, and they start at $9.97 at Lowe’s.

When buying replacement filters, check the Minimum Efficiency Reporting Value (MERV) rating number, which measures the filter’s ability to trap particles ranging in size from 3 to 10 microns. The ratings, which are an industry standard, range from one to 16, with the higher the number, the better the efficiency.

The filter you buy “depends so much on what the needs of the homeowner are,” Hollander says. “If the family has problems with allergies and asthmas, then you’re more apt to look for a higher air filtration for your home.”

The best would be High Efficiency Particulate Arrestor (HEPA) filters, he says. These filters cost $215 to $600 and are changed every three years. But these filters need equipment that should be professionally installed.

Hollander suggests people change their filters when they have to pay a bill, such as their utility bill.