Many friends know that the HEPA filter can be called the heart of the air purifier. Its material directly affects the performance and 

service life of the air purifier. What is HEPA made of? What is its purification principle? How should we distinguish the quality of HEPA? 

Why do some people say HEPA cannot be washed, while others say it can?

What is a HEPA filter?

HEPA (High efficiency particulate air filter), Chinese for "high-efficiency air particle filter", the HEPA filter can remove particles with a diameter of 

0.3 microns or more (1/200 of the diameter of a hair) with a removal efficiency of more than 99.97%. It is an ideal choice for smoke. 

The most effective filter media for dust, bacteria and other pollutants.

Many friends have a misunderstanding, that is, the larger the volume of particles, the stronger the removal ability of HEPA. In fact, this is not the case.

HEPA relies on the van der Waals force between fine particles and solids to work, so it is effective for 0.5 microns and above and 0.1 microns. 

The filtration efficiency of particles below microns is very good. Since particles of 0.1 microns undergo Brownian motion, the smaller the particles, 

the stronger the Brownian motion and the more times they are hit, and the adsorption effect is good, while particles above 0.5 microns undergo 

inertial motion. The greater the quality of motion, the greater the inertia, so the filtering effect is better.

What material is HEPA made of?

There are many kinds of materials that make up HEPA, which can be divided into (1) PP (polypropylene) high-efficiency filter paper, 

(2) PET filter paper, (3) PP and PET composite high-efficiency filter paper, and (4) glass fiber high-efficiency filter paper. Among them, 

PP (polypropylene) is paper, so it generally cannot be washed. Another part of the HEPA filter is made of PET or PTFE, which is why many people 

on the Internet claim to wash the HEPA filter. However, here I must remind you that the efficiency of PET is very low.

1. PP high efficiency filter paper

It is a new type of filter material made of polypropylene through a special hot-melt method. The product is acid-resistant, corrosion-resistant, 

high melting point, stable in performance, non-toxic, tasteless, evenly distributed, low resistance, efficient, high strength, environmentally friendly, 

etc. Features.

2. PET filter paper

It is made of melt-blown polyester resin and other materials. It has high hardness, good stiffness, corrosion resistance, high temperature resistance, 

and stable performance. It is commonly used in household appliances or large cleaning machines that do not require high filtration accuracy, 

such as sweepers and vacuum cleaners.

3. Composite filter paper (PP and PET)

Composite filter paper, simply put, is a layer of melt-blown PP, and then a layer of melt-blown PET. In this way, it combines the advantages of PP and 

PET: it is easy to form and the filtration accuracy is guaranteed; it has both stiffness and guarantee High-precision filtering effect.

4. Glass fiber high-efficiency filter paper

Glass fiber high-efficiency filter paper is a kind of filter paper with a very high gold content. It has been used in the nuclear industry before. 

Some big foreign brand purifiers, such as American Airgle, Swiss IQAir, etc., all use aluminum frames or other metal casings to fix the filter paper 

and seal it well to avoid damage and affect the filtration effect.

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