SAN DIEGO, CALIFORNIA – Too often out of sight means out of mind, especially when it comes to air filters, but heating and cooling expert Gabriel Carini says changing them on schedule is important for the residents’ health and the effectiveness and life of the unit.

“Filters keep dust and dirt from entering HVAC equipment and prevent pollutants from being spread throughout the home,” says the owner of Carini Heating, Air and Plumbing in San Diego.

The indoor comfort system ductwork functions as an expressway for pollutants like pollen, pet hair and dander, mold spores, dust mites, mildew, smoke, odors and bacteria. A high-quality air filter is what removes them from air circulation, but filters must be replaced or cleaned regularly to be effective.

“If the filter is full, it’s not catching all those pollutants and you are breathing them instead,” says Carini. “This can cause or aggravate allergies, asthma and other health problems.”

Clogged filters also make the heating and air conditioning unit work harder and use more energy to maintain the indoor temperature. Letting dirt, dust and other particles get into the equipment is basically cutting down on the life expectancy and increasing the chance of a costly air conditioning or furnace repair.

“I recommend homeowners use the most effective filters that are compatible with their home comfort systems and their budgets,” says Carini, who is an expert in residential and commercial heating and air. “They should inspect filters monthly and replace or clean them as needed.”

There are many types of air conditioner and furnace filters to choose from with different sizes, efficiencies, designs and quality. The main filter types are reusable, disposable panel, pleated and electrostatic pleated. Carini says pleated air filters are the most common because of their effectiveness, convenience and wide range of efficiencies and design characteristics. Some filters have carbon to help eliminate odors or electrostatic to more effectively attract and trap dirt. He cautions homeowners away from the inexpensive fiberglass panel filters because they are not very effective and do little to protect health or the HVAC system.

Instead of the brand or price, homeowners should look at the Minimum Efficiency Reporting Value to determine the quality of a filter. The rating system was created by the American Society of Heating, Refrigerating and Air Conditioning Engineers. The MERV rates filters from one to 16, the higher the number the more efficient the filter is at removing indoor air particles.

“A filter with a MERV 12 is the best balance between airborne particulate removal and overall heating and cooling system efficiency,” he says. “Anything higher than 12 is going to cause too much drag for the standard residential HVAC system to effectively handle.”

The system manual lists the size, recommended type and maintenance schedule for the indoor comfort system. Heating and air conditioning repair, service and installation technicians can also help homeowners determine this information. It is important to find out this information for sure because some systems have multiple filter locations and even multiple types of filters.

Measurements are typically printed on the air filter frame as height, width and depth. Sizes are standardized, but a filter that is listed as 24 x 24 x 1 will actually measure something like 23 7/8 x 23 7/8 x 1/2. Custom-sized replacement filters can be ordered online.