How Often You Should Change Your Air Filter—And What Happens If You Don’t

Changing your air filter is one of those out-of-sight, out-of-mind household chores that’s often neglected. The truth is, however, that your air filter is one of the hardest working parts of your home. “They’re designed to remove small particles, including allergen-causing microbes, dust mites, and mold spores, so they don’t recirculate through your home or aggravate allergies,” explains Sean Goddard, product manager for American Standard Heating and Air Conditioning.

When the filter becomes full of dust, dirt, and allergen particles, airflow decreases, making your system work harder than it should. Air flowing through your system may also become dirtier and prone to triggering allergy and asthma symptoms. Regularly changing your air filter will ensure the best filtration, increase the life of your machine, and give you peace of mind that you’re breathing easier. Below, Goddard tells you everything you need to know about changing your air filter.

Types of Air Filters

Not all air filters are created equally. There are three types, each with their own benefits:

Traditional Fiberglass Filters

"Traditional fiberglass filters are the flat-panel filters that have been around for years,” Goddard says. “They don’t look fancy, but they’re affordable and allow for airflow in your HVAC system.” The catch is, that they capture less than 10 percent of the airborne pollutants—but if your allergies aren’t terrible, it’s a nominal investment to give these a try first.

Pleated Fiberglass

Goddard says that pleated fiberglass filters are the most common filter type for residential HVAC. “The accordion style construction for the filter media increases surface area and filtration performance,” he explains. “Not only can it trap more particles, but it can also trap smaller particles.” The performance rating can vary, from basic whole-home coverage (typically MERV 8-10) to high-efficiency particulate capture (typically MERV 11-13) which is best suited for allergy and asthma sufferers.

Whole Home Air Filter

According to Goddard, the right whole-home air filtration system can remove up to 99.98 percent of pollutants in the air and trap particles down to .3 microns in size, including smoke, cooking smoke, and any bacteria floating around. “While these filters have the highest price tag, they also have the biggest impact on improving allergy symptoms,” he insists. Those with respiratory conditions, smokers, and homes with pets will greatly benefit from them too.

How Often To Replace Air Filter

“How often you replace your air filter will depend on filter type, usage, and environmental factors," Goddard advises. "To be on the safe side, plan on changing a standard 1-inch filter at least every 90 days. You may want to change it every 30 days if you have high system usage, allergies, or pets.” High system usage is most often a result of environmental factors such as extreme climate, wildfire smoke, pollen, pollution, and humidity.

Keep in mind that your owner's manual will provide specific recommendations for your filter.

Signs You Need To Replace Your Air Filter

Sometimes the guidelines are just that—guidelines. The only way to definitively know when you need a new filter is to do some investigating. The most obvious sign is if your programmable or smart thermostat says it’s time to change/clean the filter, but it’s not the only one. “The filter may look dirty or fuzzy, or you might notice increased allergy symptoms and dust buildup,” Goddard advises. “You may also need to replace your filter if your energy bills are creeping up but your usage is the same.”

How to Visually Inspect an Air Filter

Goddard says there are two ways to inspect your air filter, the first being to simply hold it up to a light—if you can’t see through it, it’s time for a replacement. You can also assess the color of the filter. The darker it is, the dirtier it is.

Benefits of Regular Air Filter Replacement

Goddard says that indoor air is two to five times more polluted than outdoor air, so “regularly changing your filters can be a vital step to your health and the health of your HVAC system.” Not to mention, it might just save you money.

Improved Indoor Air Quality and Respiratory Health

The purpose of an air filter is to filter particles from your air—and it can’t do that if it’s old and dirty. “Small particles in the air in your home can have short- and long-term effects on health, from irritation of the eyes, nose, and throat to more serious respiratory problems,” Goddard explains. Proper air filtration can also make a big difference for people who suffer from seasonal allergies, or who live in areas with warm-weather wildfires. 

Enhanced HVAC System Performance

When your air filter isn’t replaced regularly, your HVAC system goes into overdrive, which can cause expensive mechanical issues (and no air filtration at all in the meantime). According to Goddard, the dirt and debris could build up in your system and lead to overheating blower motors, iced-up evaporator coils, short-cycling units, and dust buildup in your ductwork.

Energy Efficiency

“Dirty or clogged filters obstruct airflow, making your system work harder than it needs to,” Goddard explains. “This can lead to dirty air bypassing the filter and collecting on the evaporator coil, reducing its heat-absorbing capacity.” In fact, he says that according to the U.S. Department of Energy, replacing a dirty filter can lower your air conditioner’s energy consumption by 5-15%.

Can You Clean and Reuse Air Filters Instead?

It depends. Permanent and semipermanent filters can be, but disposable filters—true to their name—can’t be. Because of how they’re made, trying to clean them could release the pollutants back into the air. Removing the debris from the permanent and semipermanent filters couldn’t be more simple: All you have to do is wash it off with water.