How To Clean AC & Furnace Filters (5 Simple Steps)

Do you want to learn how to clean your furnace or air conditioner filter?

There are only two types of furnace filters that require cleaning, the other is disposable and can be thrown away (here is my review on the best washable furnace filters).

In this guide, I will go over...

  • How to clean disposable filters (vacuum only)
  • How to clean electrostatic AC filters
  • How to clean electronic air cleaners for furnaces

Let's get started with this guide!

how to clean ac furnace filter

How To Clean A Disposable Air Conditioner Filter?

I would say that 95% of homes have disposable A/C filters. These common furnace filters trap dust, allergens, and fine particles as air passes through.

The only way a homeowner can clean a disposable filter would be to take it out of the furnace, and use a vacuum to clean up larger debris.

This may be a solution if you just had some work done on your home, and you know loose debris went into your furnace such as insulation or other materials. In most cases, there won't be large particles that you can remove from a disposable filter.

how to clean ac filter

These polyester and cotton filters will catch fine particles like dust and allergens, and you won't be able to clean it like you would with a disposable filter. In fact, if you did soak a disposable filter with water and washed it with a hose, it would ruin the filter --- they aren't made to stand up to such abuse.

Read Also: What Are The Best Washable & Reusable Air Conditioner Filters?

How To Clean A Washable AC Filter?

There are special furnace filters that are designed to be reusable and washable. Some of these filters can last for years if regularly cleaned and maintained.

Reusable filters are commonly treated with an electrostatic coating so that the fine dust particles are attracted to the filter. These filters use the static electricity created by air flow.

#1. Turn Off The Furnace

The first step is to turn off the furnace or A/C before removing the filter.

You don't want unfiltered air to circulate around the home while you are cleaning the filter.

#2. Remove Filter And Vacuum

With a brush attachment, thoroughly vacuum the filter.  You may be able to get buy for 30 days just by vacuuming alone.

If you are unsure, hold the filter up to a flashlight or sunlight. After vacuuming, the filter should be allowing light through.

Read Also: How Often To Change 1-Inch Furnace Filters?

#3. Spray With A Light Detergent

If your home has pets or a smoker, then it is a good idea to spray the filter with a light detergent. There are specialty sprays that are used for washable electrostatic filters.

You can also just create a mild mixture of dishwasher detergent and water. Thoroughly saturate the washable filter with the detergent and let it set for a minute.

#4. Spray Off The Filter With A Hose

If there is an arrow on the filter, then you should spray the filter in the opposite direction. Thoroughly clean the filter with the garden hose, and you should see a lot of dust and debris fall out of the filter.

#5. Let Filter Dry

Set the filter in a clean area, and let it dry for at least 10-15 minutes.

Reinstall the filter into the furnace.

Read Also:  What Are The Best Air Conditioner Filters For Allergies?

How To Clean An Electronic Air Cleaner?

Electronic air cleaners, commonly called EACs, use a high voltage electric charge that attaches to the incoming air particles.

These charged particles are attracted to the metal collecting plates. Most EACs will also have meshed pre-filters that catches larger particles.

#1. Turn Off The Furnace & Air Cleaner

It is recommended to turn off the furnace, but since it will take longer for the electronic air cleaner to dry (30 minutes), you can leave the HVAC on if you wish. Either way, the first step is to turn the power switch to the off position.

The power switch will be located on the front of the electronic air cleaner and towards the top.

Read Also: Where Is My Furnace Filter Located?

#2. Remove The Cell(s) And Pre/Post Filters

After you have removed the first electronic air cleaner, make sure there isn't a second air cleaner further inside the duct. Quite often there are two electronic air cleaners in series.

There is also usually a pre-filter which is basically an aluminum mesh filter that is designed to capture larger particles.

The main electronic air cleaner cells are designed to capture the fine dust and allergen particles.

Make sure to also remove the pre (and possibly post) filters for cleaning. The pre-filters are installed on the outside side portion of the air cleaner. If the air cleaner also has post-filters, you don't want to clean these but simply replace them.

Post-filters are not designed to be cleaned like pre-filters. Post-filters will be installed on the inside portion of the electronic air cleaner. 

Remember: pre-filters are hit with the air flow first because they capture the largest particles.

Read Also: What Are The Best Furnace Filters For Odors?

#3. Spray The Filters Outside With Detergent

Once you have taken the electronic air cleaner outside, spray it down (and pre-filters) with a mild detergent.

There are specialty made detergents for cleaning electronic air cleaners, but you can also use any type of mild household degreaser. Once you have thoroughly coated the filters with a degreaser, it is time to hose it all off.

#4. Dry The Electronic Air Cleaner & Filters

Before you re-install the electronic air cleaner and pre-filters, make sure to dry them for at least 30 minutes.

If you install the electronic air cleaner now while it is wet, it may cause an electrical short and damage the unit. The best way to dry the air cleaner is to lean it up against something at an angle, allowing the water to drain out of it.

#5. Re-Install The Electronic Air Cleaner And Pre-Filters

Once you have re-installed the filter, it is time to put the cover back on, and to flip the power switch. When the HVAC system turns on, the air cleaner's indicator light should glow.

I also recommend hitting the test button on the bottom. When you touch this button, you should hear some electrical pops, which means that it is working properly.

Read Also: What Are The Best HVAC Filters For Dust Control?

What's The Bottom Line On Cleaning Your AC Or Furnace Filters?

Most often, the homes I inspect have disposable polyester filters. These filters work great, but they have to be frequently changed and purchased which can be costly over time.

Besides disposable, there are washable electrostatic and electronic furnace cleaners. These filters will need to be cleaned regularly.

For electrostatic filters, cleaning them every 30-90 days is recommended.  It is a good idea to at least inspect the filter every 30 days to see how dirty it is.

For electronic air cleaners, they need to be cleaned at least every 6 months --- but more often if your HVAC system is used frequently.

Read Also: How To Clean A/C & Furnace Filters?

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