Have you ever done your search on Google for the best air purifier for home use?

Then, you might have come across the word ‘HEPA’.

What is HEPA Filter in Air Purifier?

HEPA stands for High-Efficiency Particulate Air filter.

The HEPA filter is used in an air purifier to eliminate particles greater than or equal to 0.3µm with up to 99.97% efficiency.

The size of a single strand of human hair falls between a diameter of 50µm to 100µm.

And, anything < 10µm diameter is not visible to the naked human eye.

So, now you might have understood how small the air particles are and the efficiency of HEPA filtration.

Air Purifier HEPA Filter

Here are the dimensions of different airborne particles.

  • Bacteria – 0.3µm to 60µm
  • Car emission – 1µm to 150µm
  • Spores – 3µm to 40µm
  • Mould – 3µm to 12µm

Initially, the HEPA filters were used in the nuclear industry in order to eliminate the radioactive particles.

Fortunately, IQAir, a Swedish Company has got the patents of HEPA technology to use in their air purifiers.

How Does the HEPA Filter Work?

HEPA filters comprise a filter sheet of randomly placed fibers with diameters between 0.5 and 2 micrometres.

Its functionality is based on three factors – diameter of the fiber, thickness of the filter and face velocity.

HEPA Filter is designed in such a way that it catches the smallest of particles and pollutants in the air by making use of the following mechanisms.


The particles present in the air stream that come within one radius of a fibre will adhere to it.


The air changes its flow as it reaches the filters and the larger particles get filtered easily. The higher air velocity and lower fibre separation results in a higher impaction.


This method is efficient in filtering the particles less than 0.1µm in size.

  • HEPA filters can remove up to 99.97% of the pollutants present in the air that are greater than 0.3µm
  • They can clean and purify the air inside your room very effectively
  • Removes dust and debris to a great extent
  • Can’t clean air with chemicals, fumes, gas molecules, and odours
  • HEPA filters are usually expensive


HEPA filters have got many advantages but at the same time they’re expensive too.

Since this is a new technology in India, most air purifier brands have been using gimmicks like adding extra parameters to the word HEPA in order to show that their product is unique.

There are actually 5 types of HEPA filters starting from A to E, with HEPA-A being the least effective filter of all, whereas the HEPA-E has got higher efficiency.

So, next time, you go shopping for air purifiers with HEPA filters, you should choose wisely.