How Does Air Purifier work?

In this post, you will find how air purifier works.

The working principle of air purifier is really simple.

Every air purifier has 2 basic components in it- A Fan and Filter.

A fan in an air purifier is designed to pull in air from the surrounding. Then it forces the air to pass through various stage of the filter.

The air then passes through the filter of the purifier; the pollutants and allergens get blocked in the filter and then it produces non-polluted fresh air.


Types of Air Purifier

There are generally two types of air purifier- Active and Passive.

The active air purifier uses ionizers. Active air purifier releases negative ions to air and these ions stick to dust particles and airborne pollutants. They do their work but the problem occurs when they release ozone(o3) and ozone is a hazardous gas and regular inhalation of ozone may lead to severe damage to your health.

You can read here to know why ionizers are not good for your health.

In comparison, passive filters use harmless and more conventional air filtration technology to clean the air. They normally use a fan and a multi-layered filter.

Filters used in an air purifier

The filter of an air purifier does all the trapping of air pollutants.

Many air purifier comes with a different stage of filtering system to trap different airborne particles because a single filter cannot block all the particles.


Most of the air purifier uses 3 stages of filtration method.

air filtration method of air purifier

Pre Filter or Primary filter

A Pre Filter or Primary Filter in an air purifier is designed to capture larger particles such as dust, soil, pet dander or hair. Pre-filter acts as the first line of defence in purifying the air from your room.

They also help in increasing the life of next stage filters such as HEPA filter and Carbon activated filter.

The air output from the Pre or Primary filter is then passed through the next stage of filter i.e either a HEPA Filter or Carbon Activated filter.

Pre-filters can be


-non-washable and

-combined with HEPA-Activated carbon filter.

A washable pre-filter can be taken out from the air filter when it catches too much dust and wash it out. However non-washable filters are cheap compared to a washable pre-filter.

Some pre-filters are clubbed with HEPA or Activated carbon filter and you need to replace the whole filter when its life gets over.

HEPA Filter

HEPA filter or High-Efficiency Particulate Air filters are one of the best filter used in an air purifier. They have an efficiency of 99.97%

This means a HEPA filter is able to trap 99.97% of particles of size 0.3 microns.

A micron or micro-meter is a unit of length. A human hair is typically 100 micron in size and a HEPA filters are able to trap particles that are 300 times smaller than a human hair.

HEPA filters are designed to trap microscopic pollutants, allergens, pollen, PM(particulate matter) 2.5 and PM 10 particles.

Particulate matters are tiny particles suspended in the air. They are small enough to pass through our nose and throat to deep into our lungs. Prolonged exposure to PM particles can lead to a severe health condition such as asthma, heart disease, reduced lung function, bronchitis, etc.

PM 2.5 are particles of size 2.5 microns and PM 10 are of size 10 microns.

Since a HEPA filter is able to trap particles of size up to 0.3 microns, that means it is capable of filtering out particles that are of size 10 times smaller than PM 2.5 and 30 times smaller than PM 10.

Activated Carbon filter

The air that comes out from a HEPA filter is often fed to a carbon activated filter.

A carbon activated filter with the help of a bed of activated charcoals removes odor, gaseous pollutants, Volatile organic compounds(VOC) and formaldehyde.

Image credit: Macrovector

Once the air from the last stage of the filter comes out, it is again then pulled in by air purifier for further cleaning. After a few repeated cycle, the air gets cleaned from all type of pollutants that is fresh and harmless to breathe.

So, this is how an air purifier works protecting you from the harmful gaseous pollutants suspended in the air.

I hope you have liked this post, if you have any questions, you can put it on the comment section below.


A blogger who loves to write about things that add value to the readers. He is more of a solution provider rather than a typical content writer. You can contact him at

Leave a Reply

Your email address will not be published. Required fields are marked *