What is a Pre-filter? Can You Wash it?
Short answer
Pre-filter capture large particles and protect the inner filter.
What Is The Function of A Pre-filter
As the name implies, a pre-filter or panel filter is the initial, first-stage filtration in an air purifier. It traps unwanted large airborne contaminants from passing through 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 a carbon pre-filter comes attached with 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 first block out all the large irritants from the air. 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-filter | HEPA Filter | |
| Efficiency | ||
|---|---|---|
| 20-70% efficiency on particles as small as 3-10 microns. | 99.97% efficiency on particles as small as 0.3 microns. | |
| MERV | ||
| 1-8 | 17-20 | |
| Filter Density | ||
| Low | High | |
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 is very good at trapping dust. But dust gets piled up quickly, and it is uneconomical to replace the filter constantly. 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 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 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, speakers, and even in a laptop. So many of these devices even fit in a pre-filter to reduce the number of inflowing dust.
