What is a Pre-filter? Can You Wash it?

A mechanical air cleaner requires a different set of filters to clean the air. No exception with a first-stage pre-filter. It might be outshined by HEPA filter in terms of efficiency, it will still play a big part in the purifying process. Besides acting as a protector for other filters, there are a lot more hidden perks in having a pre-filter. What are the so-called hidden perks you might ask? Let's go deep and find out.


Even though the HEPA filter outshines in terms of efficiency, pre-filters exist in our everyday items more than you could ever imagine. It is in HVAC, furnaces, or ventilation systems to block out airborne pollutants. It can also be found in the least expected places, from masks, respirators, speakers, and even laptops, to reduce the number of inflowing dust.

What Is The Function of A Pre-filter

As the name implies, a pre-filter or panel filter is the integral, first-stage filtration in an air purifier that plays a big part in the purifying process. A pre-filter traps large airborne particles e.g. dust, hair, debris, insect, and large mold/ pollen, from passing through to the next stage. It protects the HEPA filter from getting clogged or damaged by contaminants. Most pre-filters are rated between MERV 1-8 with a filtration efficiency between 20-70%. It can capture coarse particles between 3-10 microns. If a carbon pre-filter comes attached to a carbon sheet, it will even filter out light smoke and odors.

Another function of the pre-filter is to extend the HEPA/ carbon filter lifespan. The pre-filter will block out all the large irritants from the air, freeing the inner filter from getting clogged dust, hair, and other irrelevant particles. The protected HEPA filter can now concentrate solely on microscopic particles that bypassed the pre-filter.

Pre-filter VS HEPA Filter

Pre-filterHEPA Filter
20-70% efficiency on particles as small as 3-10 microns.99.97% efficiency on particles as small as 0.3 microns.
Filter Density

Can You Clean Or Wash Pre-filters?

You can gently soak and wash most re-washable pre-filter, but check the product manual to be on the safe side. Some pre-filter only allows light vacuuming to avoid damaging the filter’s density. Pre-filter is very good at trapping dust. But dust gets piled up quickly, and it is uneconomical to replace the filter constantly. Therefore, most reusable pre-filter is made of fiberglass, pleated panel, or steel. In other words, they are permanent filter that can withstand cleaning without affecting their efficiency. Some manufacturers even quoted their permanent pre-filter will last a lifetime. Still, in our experience, 5 years is a good take. As for a 2-in-1 carbon pre-filter, never wash it, as the water will damage the activated carbon. You will need to replace the filter periodically as a typical HEPA filter.

Max Fernandez

A loving father and a dedicated reviewer for airfuji.com with more than 1000 air purifiers under his belt. Max Fernandez is also one of the million patients currently suffering from asthma. Feel free to nudge him if you have any questions.
How Can I Help You Today?

I need air purifier that is to deal with for to be placed in the for with