“Stay Indoors” is what the government and the news channel advice whenever the pollution reaches a higher level in the cities.

While walking down a busy road in an urban city, we often cover our nose and mouth to protect ourselves from dust and pollution.

Sometimes, we even wear a mask during the winters.

And we speed up our pace to reach our homes or offices because that’s where we know that we’ll be safe!

But, just being inside the home does not mean that you are safe. Staying indoors is good advice only if you have an efficient air purifying system in your home.

You must have heard about an Air Purifier. If you do basic research on air purifiers on the internet, you’ll come across a word, HEPA.

It is an essential and popular air purification method.

So, let us delve into the concept of HEPA in air purifiers.

What Does HEPA Mean?

HEPA stands for High-Efficiency Particulate Air.

It is used to describe the filters which can trap 99.97% of the particles, which are 0.3 microns or larger.

What Is The Importance Of ‘0.3 Microns’ Here?

Scientists refer the micron size as MPPS (Most Penetrating Particle Size).

The particles with micron-size evade the air filters more than the larger particles.

Therefore, if a filter claims that it can trap 99.9% of the large particles may be weak at capturing the ultra-fine particles.

Similarly, if a filter touts that it can trap ‘smallest’ of the particles, it isn’t telling you ‘how much small’ particles it can capture! It doesn’t tell if it can trap 0.3 microns sized particles or not, which are the most dangerous and the hardest one to filter.

Let us look at the size of various airborne particles:

Spores 3 to 50 microns
Molds 3 to 12 microns
Bacteria 0.3 to 60 microns
Emissions from a Car 1 to 150 microns

Anything which is less than 10 micrometre cannot be seen through the naked eyes.

Why Is It Important To Remove Such Small Particles From The Air?

As discussed above, scientists refer these fine particles as MPPS.

Larger particles such as pollen, mould spores, etc. are filtered out in the nose and throat.

But, some microscopic particles easily enter into the lungs and may damage our health. It may carry pathogens of severe disease. Patients of allergies and Asthma suffers the most.

So, it is essential to filter out large as well as small particles from the air.

What Is A HEPA Filter?

HEPA is a type of high quality air filter which meets the HEPA filter standard.

A HEPA filter removes the smallest of the particles. Along with 0.3-micron-sized particles, it is even more efficient at removing at PM 10, PM 2.5 and the larger ones.

Cleaner The Home, Better The Peace Of Mind

We take around 23,000 breaths every day.

Though we might not be able to control where we live, we can have some control over what we breathe.

This small change in your home can result in a significant improvement which will ensure clean and safe air for you.

Frequently Asked Questions

1. How Does HEPA Filter Work in an Air Purifier?

HEPA consists of thousands of glass fibres which are arranged into a mat. They possess a diameter of 0.5 – 2.0 micrometres.

The three key factors which affect its function are:

  • The diameter of the fibre.
  • The thickness of the filter.
  • Velocity.

As the particles pass through the fibrous web, they are filtered out in the following ways:

Direct Impaction

The air changes its flow as it reaches the filter. More massive particles like dust, mould and pollen can’t follow the curving path of the air stream. Hence, they travel in a straight way, collide with the fibre and stick to it.

Higher the velocity of air, higher is the impaction.


The airstream carries a particle between the two fibres. If the size of the particle is larger than the gap between the fibres, it gets entrapped.


The flow of air is active enough to re-route its path around the fibres. But, with the moment of inertia, particles continue their way and stick at the fibres.


This method works on the principle of ‘Brownian Movement.’

This method filters the smallest of the particles, especially less than 0.1 micrometres in size.

When these fine molecules collide with the gas molecules, they get slow down. It entraps the particles either through Impaction or Interception.

This method works best at the lower air velocity.

2. What are the types of HEPA Filters?

Depending upon the efficiency, HEPA filters have been classified with A to E stickers.

Type A is considered the least efficient, while Type E, the most valuable.

Generally, Type E HEPA is used in defence-grade applications.

Vacuum cleaners make use of Type A HEPA filters which works well within our house.

3. What are the Pros of Using HEPA Filters?

It captures both small and large particles, thus gives fresh and clean air.

It keeps away 99.97% of the pollutants of minute size. So, even the dust has no chances against the HEPA.

These are available in different sizes and cost to match the budget of your wallet.

4. What are the Cons of Using HEPA Filters?

Some of the HEPA filters are washable while others are not. They can just be replaced, which is a costly affair.

Replacement of the prior HEPA filters with the branded quality filters shells out huge money.

The filters need utmost care while cleaning and installing.

A HEPA filter cannot remove gas molecules, fumes and odours, whose size is less than 0.3 micrometres.

5. What are the reasons to Choose a HEPA Filter?

HEPA filters are worth buying these days as the pollution has increased to a high level. Though they are expensive, they provide value for the money you invest in buying them.

Apart from the ‘Air Pollution’ other reasons to choose a HEPA filter are :

Pet Owners

Removing pet danders from the air saves you from allergy symptoms. An Air Purifier with both a HEPA and a Carbon filter removes allergens and odours.

New Parents

Parents concerned with airborne pollutants should consider an air purifier with HEPA filter. Since a baby’s lungs are very delicate and are still developing, the presence of airborne particles may impact his health and hamper the natural growth.

Asthma Patients

By choosing a good HEPA air purifier for home, Asthma and allergy patients can enjoy refuge from the unpleasant symptoms of the disease.


There are many sources by which you can buy a HEPA Filter Air Purifier. Many kinds of air purifiers are available in the market, which makes use of different technologies.

Some use HEPA, Carbon, UV, Vitamin C Filters and many more.

Buy only the best quality product from reliable sources.

Avoid buying ‘HEPA-type’ or ‘HEPA-like’ filters. These do not provide the best results as compared to a True HEPA filter.