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Home Air Filters & Air Conditioner, Furnace & HVAC

HVAC filters fit into your air handling system to clean the air of dust and dirt. Should the ignition ports of your furnace become dirty, it may not fire at all.

If your filters are clogged, airflow is limited and the HVAC system will function inefficiently.

Keeping your filters changed on a regular basis will protect your system from damage and your home from temperature extremes caused by HVAC failure.

Benefits Of Changing Filters

The filter on your HVAC system captures dust and allergens from the air. These filters can also sweep up other contaminants that get swept into air returns, such as pet hair.

There are also filters you can add to your HVAC unit that will pick up and neutralize the odor of cigarette smoke.

A forgotten or over-looked filter can also heavily impact the functioning of your furnace or air conditioner.

Air can’t move smoothly through a clogged filter, and older units have been known to pull overloaded filters into the blower mechanism, causing a catastrophic failure to the system.

When determining how often to change HVAC filter, remember that a small investment in filters requires much less cash than the large investment in furnace repair and replacement. Set a date and change your filter!

Filter Features & Specifications

Furnace filters are available in different grades and pick up a variety of particles and particle sizes.

Your HVAC filter replacement can be basic, such as a fiberglass filter designed to protect the furnace from debris, or you can clean the air in your home with an electrostatically charged filter.

The five different construction types are as follows:​

  • Fiberglass: Fiberglass filters are well suited to protecting your HVAC system from contaminants but won’t do much to protect your lungs. These filters are generally inexpensive but filter only 2% of submicron particles.
  • Washable / Reusable: These filters must be taken out and hosed off before reinstalling them. They can be sprayed with a sticky substance to make it easier for them to capture more particles, but only offer 6% capture of the submicron particles in your home.
  • Pleated Polyester: The depth of the pleats is a pretty good indication of the quality of the filtration available; the deeper the pleat, the better the capture. Thin pleats will clear up to 11% of submicron particles and deep pleats will capture up to 25%.
  • Electrostatic / Electronic: Electrostatic filters are built of electrostatically charged materials and can capture up to 49% of submicron particles. Electronic filters actually move air through an electrostatically charged grid for a removal rate of more than 90%. It’s important to note that electronic filters need a power source and require detailed maintenance to avoid failure.​

Furnace Filters and Mold

Mold spores can be brought into your home via outside air and can be filtered out with a highly efficient furnace filter, such as a deeply pleated design.

An additional HEPA air purifying filter is also a good option to reduce the risk of airborne mold spores.

A Word About Pets

Pet dander is a common allergen and is shed from the skin of your pets. Furnace filtering systems have little chance of capturing this dander.

However, by investing in electrostatically charged filters both on your HVAC system and on your vents, you can have an impact on pet dander.

You will need to leave your blower motor set to “on” instead of “auto” to have the biggest impact.​

Other methods of reducing pet dander including using a HEPA vacuum cleaner and investing in a portable air cleaner.

Types Of Filters & Replacement Requirements

How Often Should I Change My Furnace Filter?

Dirty and Clean Home Air Filter Comparison

It’s critical to set a schedule to remind you when to change air filters. Your HVAC filter can be easy to forget because many filters only need changed every three months.

As previously stated, replacing air filters monthly in the summertime is a great choice to keep that cool air flowing.

If it’s easier for you to remember, change it monthly all year long.

It may cost a bit more, but your equipment will be protected and the air quality of your home will be improved.​

It’s important to note that your central air filter replacement is your furnace filter. All of the ductwork that carries warm air when the furnace is working also carries cool air once the air conditioner fires up.

Your furnaces filter lines up where the air duct meets the furnace. You’ll sometimes find this filter in a vertical slot beside the furnace; sometimes in a horizontal slot on top of the furnace.

There should be a metal cover over the furnace filter slot, and often these panels let you know what size of furnace filter to purchase.

How Often Should I Change My AC Filter?

For a window or a portable A/C unit, check the condition of the pull-out filter before you turn on the unit and monthly thereafter.

Your window a/c unit should be cleaned with warm soapy water, or you can use white vinegar if you prefer. Let the filter dry completely before replacing it.

If you have a window air conditioner, your manual should let you know where the filter can be found. Pull and rinse or replace this filter as suggested by the manufacturer, or monthly at the least.

Per experts with This Old House, changing out your HVAC filter during summer months is a great idea for efficient delivery of cool air!

Air Vent Filters​

Vent filters attach to the bottom of your floor or wall vents to prevent contaminants from the vents from blowing into your home.

For those with household members that suffer from asthma or other sensitivities, adding an activated carbon filter panel to your vents can be life-changing.

These panels are often sold in sheets and can be cut to fit your vent configuration. They should be changed monthly.

How To Change & Dispose Of Your Old Filters

filter air flow direction

The more efficient the filter you buy, the more care you’ll need to take when disposing of it.

The filter will be loaded with dirt and dust which you’ll want to capture, rather than drop on the floor near your furnace.

The following instructions on how to replace an air filter work with the same with many furnaces and air conditioners.


  1. Turn off the unit. You don’t want it to start without the new filter in place.
  2. Get a trash bag ready to wrap up the old filter.
  3. Extract the old filter slowly and put it in the trash bag. There will be arrows on the filter casing that will indicate air flow; note the direction of those arrows so your new filter goes in facing the right direction.
  4. Remove your new filter from the plastic sleeve and place it in the filter slot with the air flow arrows match the direction of the old filter.
  5. Turn on the system.
  6. Seal up the bag with the old filter and discard to the appropriate waste management system.​

Final Thoughts

Keeping your HVAC filter changed consistently will protect this expensive investment and keep debris and dust out of the equipment. With the right filter purchase, you can also improve the air quality in your home.

Consider investing in one of the more efficient filter panels, such as a deeply pleated filter.

If you’re trying to clear away a particular odor such as cigarette smoke, an active carbon filter may be a better choice.

Be aware that furnace filters can only capture what is airborne, so pet dander may not be swept up in your HVAC filter.