Understanding the basics of appliance air filters.
‘Refrigerator making humming sound,’ ‘dryer not drying,’ ‘vacuum cleaner loss of suction,’ ‘air conditioner not cooling,’ ‘HVAC system making noise,’ etc. are some of Repair Clinic’s most searched symptoms and most-watched Troubleshooting videos.
Often, seemingly complex appliance problems that might require expensive and laborious repairs aren’t anything more than a clogged or wore-out filter. Regular filter replacement is vital for your appliances’ maintenance and life expectancy and crucial to your family’s health.
Any appliance with a filter that cleans air needs attention. Regular filter replacement is paramount to keeping appliances in good working condition. Appliance filters are relatively easy to change compared to other appliance and power equipment repairs and are the first part you should check when something seems wrong or off with your appliance or equipment.
Home appliances that have air filtration systems include air purifiers, range hoods, over-the-range microwaves, clothes dryers, vacuum cleaners, dehumidifiers, room air conditioners, HVAC, central air systems, and gas furnaces.
Air filters work by trapping small particles of dirt, debris, and impurities like food particles, dust, pollen, and other pollutants from getting into your home’s air supply. Air filters are designed to prevent harmful irritants and inhalants from contaminating the air you and your family breathe.
Indoor air contains pollutants that can affect human health. Some of these
pollutants come from the outdoors, and others come from indoor sources
and activities, such as cooking, cleaning, secondhand smoke, building
materials, consumer products, and home furnishings. These indoor air
pollutants can be particles or gases, including volatile organic compounds
(VOCs). Common contaminants that can be found indoors include particulate
matter (including PM2.5 [fine] and PM10 [coarse]), formaldehyde, mold,
and pollen. The indoor air quality will vary from home to home and over the
course of a day within a home. Since most people spend about 90% of their
time indoors, mostly in their homes, much of their exposures to airborne
pollutants will happen in the home. The most effective ways to improve your
indoor air are to reduce or remove the sources of pollutants and to ventilate
with clean outdoor air. In addition, research shows that filtration can be an
effective supplement to source control and ventilation.
The EPA’s Guide to Air Cleaners in the Home
The types of air filters most commonly used in homes and appliances are known as mechanical air filters. Mechanical air filters work by trapping particles from the air onto the filter and can trap everything from dust to cockroach allergens and pet dander, but they don’t trap gas or odor.
Mechanical filters often have pleated fans to force air through a dense web of fine fibers that trap particles. Filters with very fine mesh are called HEPA (High-efficiency particulate air) filters—those certified to collect 99.97 percent of particles of a specific size (0.3 microns in diameter—smoke and paint pigments). HEPA filters can remove larger particles, too, including dust, pollen, and some mold spores while they’re suspended in the air. (Note that some filters labeled “HEPA-type” or “HEPA-like” have not been certified to meet the requirements of a true HEPA filter but may still perform adequately in our tests.)
A second standard type of home appliance air filter is sorbent, activated carbon filters. Rather than catch particles like mechanical filters, sorbent filters use activated carbon to adsorb some odor-causing molecules from the air. They may also tackle some gases, but they’re not particularly effective against formaldehyde, ammonia, or nitrogen oxide. Because they don’t combat particles, many appliances will include an activated carbon prefilter and a pleated filter for catching particles. Activated carbon gets saturated faster than a pleated filter, though. It requires replacement more frequently—every three months instead of every six to 12 months like recommendations for pleated filters and mechanical filters.
Home Appliances with Air Filters
Most air purifiers have a filter indicator (often a light) that alerts you when the filter should be checked and possibly replaced. Though you can simply wipe down most prefilters, the primary HEPA filter should be replaced about every six to 12 months, or as your manual advises.
Central Air Conditioners & Heating Systems
If you have a combined forced air heating and cooling system, follow the filter manufacturer’s recommendation on how often to change it. In general, the thicker the disposable filter, the less frequently it needs to be changed. Washable filters usually require monthly cleaning, but according to testing done by Consumer Reports, none of the washable filters currently on the market have performed very well, so the well-respected organization does not recommend them.
A dirty lint filter can extend drying time and lead to lint buildup in the dryer’s cabinet and duct, creating a fire hazard. In addition to cleaning the lint filter between loads of laundry, inspect the duct and cabinet every few months to check for lint buildup or heaviness in the flexible exhaust line. Some newer dryers have blocked vent sensors that detect reduced airflow, but according to Consumer Reports, sensors often don’t perform consistently, so it’s best to inspect the venting yourself.
As with a central AC system, a dirty filter can prevent airflow, leaving the equipment struggling, so replace a disposable one as the manufacturer advises. Most models will need to be changed roughly every 3-12 months. Dirty furnace filters can also contribute to noise and dysfunction in your HVAC system, leading impressionable and imaginative minds to hear ghostly noises and experience hot and cold spots throughout a home. When you remove the old filter, take note of the size and the arrow that indicates the direction of the airflow; both should be printed on the filter. One of the biggest mistakes people tend to make is putting the new replacement filter in backward. #RCTechTip: take a picture of the arrow direction and size with your phone before you remove your furnace filter. Learn more about air filter maintenance and how to pick a furnace filter.
Humidifiers / Dehumidifiers
De/humidifiers are one of the most straightforward home appliances to clean but can also be one of the most hazardous if dirty filters are ignored. A quick cleaning will improve air quality and the machine’s performance, especially when humidity levels rise above 50 percent, which can lead to the growth of dust mites, mildew, and mold on your filter. (If you see any of those, it’s time for a new one.) Dirty reservoirs and filters in humidifiers can quickly breed bacteria and mold. Dirty humidifiers can be especially problematic for people with asthma and allergies. Even in healthy people, humidifiers can trigger flu-like symptoms or even lung infections when the contaminated mist or steam is released into the air. Evaporators and steam vaporizers may be less likely to release airborne allergens than many cool-mist humidifiers. For more health-related guidance on dehumidifiers and humidifiers, refer to the mayo clinic’s FAQ article. In 2017, TIME Magazine published a humidifier horror story that is also an informative read.
Range Hoods & Over-the-Range Microwaves
A filter with grease buildup results in a fan that can’t exhaust properly or capture cooking fumes, leaving a sticky film on appliances and kitchen walls. Some models have filter maintenance lights; if not, check and clean the hood filter every 1-3 months, or more often if you cook frequently or like to fry. Slide the filter out of the range hood and into a sink filled with hot water and a good degreasing soap. Let it soak for at least 10 minutes. Use a sponge to remove any remaining grease or debris carefully. Then air-dry and reinstall. If a good cleaning doesn’t get the grime off and looks, smells, or feels greasy, it’s time to replace it. Some over-the-range microwaves have dishwasher-safe filters, which makes for easy cleaning. Countertop microwaves do not have filters, so no need to worry about that appliance filter.
Room / Window Air Conditioners
All window units have a filter, and many come with a filter indicator that signals when it needs cleaning to keep cooling your home efficiently. If yours doesn’t, check the filter at least once a month during periods of heavy use or year-round if you live in a warm climate. Remove the filter and use your vacuum’s upholstery brush to suck up any heavy dirt, then wash the filter using a mild solution of dishwashing liquid and warm water. It’s best to wait until it’s dry to reinsert to make it easier on yourself and to let it dry properly.
Failing to change the filters in your vacuum cleaner may cause it to lose suction or, worse, spew dust back into the air or deposit it back onto your floor. Changing the filters regularly, especially on bagless models, saves work and aggravation. Like air purifiers, many vacuums have a prefilter and a primary filter; check your model and owner’s manual for more information and instructions.
Repair Clinic offers more than 100 Troubleshooting, How-To, and Part Replacement video tutorials on appliance air filters; click to learn more.
So, filter through the abundance of supportive online resources, filter out any excuses or objections — and go check and change your appliance filters!