HEPA Filter Maintenance

Can you wash a HEPA filter, or will it diminish the filter’s cleaning efficacy?

HEPA filters claim to remove particles like dust, allergens and mold spores from the air, but they lose any effectiveness once they become clogged with debris. Once saturated, they will begin to release pollutants trapped on the filter surface back into the air.  However, with HEPA filters being used in vacuum cleaners, air purifiers and HVAC systems, replacing them can become a major expense. Also, finding and ordering filter replacements can be an arduous process or generate more waste. These are legitimate concerns, and you may wonder how to clean a HEPA filter instead of replacing it numerous times.

The answer is not as straightforward as it may seem. This article will look at what HEPA filters are made of and examine different types of HEPA filters to better understand if they can be cleaned, and if so, how to do it properly to ensure the filter continues to function according to its claims.

What are HEPA filters made of?

HEPA filters, or high-efficiency particulate air filters, are defined by how well they have been rated to filter particles, not by how they are made. To meet the HEPA standard, a filter is estimated to remove 99.97 percent of particles that are 0.3 microns (or micrometers) in size from the air that passes through them, though this means that particles smaller than 0.3 microns can escape the HEPA filter.

In practice, HEPA filters are made from a variety of materials, including “coarse glass fibers, coated animal hair, vegetable fibers, synthetic fibers (such as polyester or nylon), synthetic foams, metallic wools, or expanded metals and foils,” according to the EPA. These fibers are tangled together randomly and compressed into paper-like sheets. The sheets are pleated to increase the surface area that the air passes through, and mounted onto a frame made of cardboard, plastic, wood or metal. Manufacturers might add other elements to a HEPA filter, such as a pre-filter to screen out larger particles, activated carbon to help remove odors and gases or a chemical treatment to make particles stick to the fibers.

Where are HEPA filters used?

Originally, HEPA filters were used in research and industrial facilities, because they were developed specifically to remove radioactive particles from the air in nuclear testing labs. Today, HEPA filters show up in a variety of consumer products.

• Air purifiers
• Vacuum cleaners
• HVAC systems
• Cars

How is a  HEPA filter used?

Indoor air quality is a major concern, especially for people with sensitive immune systems such as infants or the elderly. Particles like dust mites (and their feces), mold spores and other allergens in the air may trigger health symptoms such as allergies or asthma, and people search for a way to remove them from the air using filter media in a portable air purifier, special vacuum or HVAC system. One type of filter is a HEPA filter.

A HEPA filter in your HVAC system, air purifier or vacuum cleaner is designed to only filter particles (and not gaseous pollutants such as those in smoke) from the air in an effort to improve air quality. Limited studies have indicated that air purifiers with HEPA filters may help reduce the amount of particulates in the air to improve the overall air quality (Laumbach, Meng, & Kipen, 2015). However, many harmful pollutants, like airborne chemicals or particles in smoke, are much smaller than a HEPA filter can trap. There is also a possibility that given all the particulate matter (dust) that collects on a HEPA filter, it can provide the right conditions for mold growth. It was documented in a study in Korea that mold can grow on a HEPA filter (Kim et al., 2014) and potentially release back into the air.

Can you clean a HEPA filter?

If your HEPA filter is not specifically labelled as washable or “permanent,” then the answer is no. You can rinse the filter in water, tap excess dust off of it or remove some dust with a vacuum, but this can definitely damage the mesh of fibers that allows the filter to remove particles from the air. Even if the filter looks undamaged, some of the fibers will be broken or stretched out. You will end up with a somewhat clean looking filter that does not do the job of filtering properly.

What allows a HEPA filter to meet its claims is the consistency of the “weave” of glass fibers. If the fibers are stretched or torn, it will create gaps in the filter large enough for particles to pass through. The integrity of the frame is important as well. If the frame itself or the gaskets that provide a seal between the frame and the location it is mounted in are compromised, air can flow around the filter instead of through it.

If the filter is marketed as being washable or permanent, then it is possible that you can wash it or clean it off and it will still function. However, there is no standard for washable HEPA filters, and there have not been studies testing how well these filters work after they have been washed. It is possible that the manufacturer has found a method of making filter fibers that will not be damaged by cleaning, but there really is no way of knowing for sure, so you are taking your chances.

Why might cleaning a HEPA air filter be a bad idea?

As discussed, cleaning a HEPA filter almost certainly will cause damage to the extremely fine mesh of fibers that allow the filter to do its job. But even if you could be 100 percent sure the filter would not be damaged by cleaning, there are other reasons that cleaning a HEPA filter is not a great idea.

• Cleaning a filter is a dirty job. Unless you take the filter outside to clean it, there is a good chance that the act of cleaning it will introduce some airborne pollutants to your house. Getting rid of those pollutants is the reason you may want to use a HEPA filter in the first place. The pollutants introduced back into the air may include any microbial growth that has taken place on the filter.
• You may inhale some of the pollutants from the filter. Even if you can clean your HEPA filter outdoors, some of the particles from the filter will be in the air while you clean it. Unless you wear some type of respirator, you can inhale those pollutants, which could trigger an allergic reaction.
• You will need a filter for your filter cleaner. If you use a vacuum to clean out a HEPA filter, the vacuum will also need to have a HEPA filter, or it will not be able to keep the particles from the dirty filter in the canister. It will disperse all those particles into the air. And if the vacuum does have a HEPA filter, what will you use when it is time to clean that one?
• The filter must be completely dry before using. A wet HEPA filter could further allow mold to form on the filter surface. Because of the fine mesh of fibers in a HEPA filter, they take a long time to dry (manufacturers recommend at least 24 hours). The whole time the filter is drying, you are not filtering air.

How to clean a HEPA filter if you have to

The general recommendation is that HEPA filters should be replaced, not cleaned. But if you absolutely have to clean a HEPA filter, there are two ways to do it. Which method you use depends on what type of HEPA filter you have. Because there are no official standards for cleanable HEPA filters, there are no defined terms for the types of cleanable filters available. However, manufacturers have adopted certain marketing terms with some consistency: washable and permanent.

A washable HEPA filter should be cleaned by rinsing it under cold water. You should be careful not to touch the filter material, only allowing it to come in contact with water. Allow the filter to completely dry before reinstalling it. Some filters have special instructions. For instance, some canister type vacuum filters should only be washed on the outside of the filter, being careful to avoid getting the central part of the canister wet.

A HEPA filter marketed as “permanent” should be cleaned by gently using a vacuum cleaner to suck away dust and debris from the surface of the filter. Water should not be used on these types of filters.