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.
Short answer
Pre-filter capture large particles and protect the inner filter.

What Is The Function of A Pre-filter

As the name implies, pre-filter or panel filter is the initial, first-stage filtration in an air purifier. It is used to trap unwanted large airborne contaminants from getting pass to the next stage. Most pre-filter are rated between MERV 1-8 with a filtration efficiency between 20-70%. It can capture particles between 3-10 microns. This includes dust, hair, debris, insect, and large mold/ pollen. If is a carbon pre-filter that comes attached with a carbon sheet, it will even filter out light smoke and odors.

Another function of pre-filter is to extend the HEPA/ carbon filter lifespan. The pre-filter will first block out all the large irritants from the airway. This allows the inner filter to be free from dust, hair and other irrelevant particles. The 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 just to be on the safe side, check the product manual. Some pre-filter only allows light vacuuming to avoid damaging the filter’s density. Pre-filter are very good at trapping dust. But dust gets piled up quickly and is uneconomical to constantly replace the filter. Therefore, most re-usable pre-filter is made of fiberglass, pleated panel or steel. In other words, they are the permanent filter that can withstand cleaning without affecting its efficiency. Some manufacturers even quoted their permanent pre-filter will last a lifetime but 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 periodically replace the filter as a normal HEPA filter would.

We all frequently associate pre-filter will HVAC, furnace or ventilation system, it can also be found in the least expected places. From masks, respirators, speaker, and even in a laptop. The reason so many of these devices even bother fitting in a pre-filter is to reduce the number of dust from inflowing into the devices.

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.