When we think of purchasing the best air conditioners in India, we look at its BEE rating. Air filters too have an efficiency standard. It is called High-Efficiency Particulate Air or HEPA.

There are two HEPA standards- European and the U.S. In order to meet HEPA standards; air filters must be able to remove, 99.95% (European) or 99.97% (U.S standards) of particles from the air that passes through. The particle diameter that the filter should be able to remove should be less than or greater than 0.3 microns.

How does a HEPA filter work?

These filters are composed of a mesh of haphazardly put together fibers, which are made of fiberglass. The diameters of these fibers could be anywhere between 0.5 and 2.0 micrometers. HEPA filters are intended to target much smaller pollutants and elements.

How does a HEPA filter work
img source: https://en.wikipedia.org/wiki/HEPA

Using a combination of three mechanisms, these elements stick to a fiber. They are:

  1. Dissemination
    Smallest particles collide with gas molecules, thus delaying their path through the filter.
  2. Intervention
    When elements flowing in a line through the air stream come within one radius of fiber, they stick to it.
  3. Impact
    Due to the curving shapes of the air stream, the larger particles are unable to avoid fibers and stick to them directly. As the airflow velocity increases and fiber separation diminishes, this effect increases.

What happens when HEPA filters malfunction?

If the particles penetrate the filter, then there are other technologies that work in tandem with the HEPA filters and capture micropollutants like smoke, chemicals, etc.

True HEPA better than HEPA?

Marketers these days use different terminology to describe air filters. True HEPA is a term used to differentiate between the U.S and European standards. Any other terms like “HEPA type”, “Ultra HEPA”, and any other variations aren’t recognised by either of these accrediting bodies.

Usage of HEPA filters

These filters are used in manufacturing areas where contamination control is required, like – semiconductors, nuclear, disk drives, hospitals, etc. These days HEPA filters are also used in the manufacture of consumer products like cars, air conditioners, and best air purifiers.

Are these filters useful if one has allergies?

Dust mites, pollen, etc. present inside the air circulating in your house can be a cause for your allergies too. The best air purifiers in India use HEPA filters, which can be helpful in bringing you the much-needed relief from your allergies. These air purifiers are small, portable units. Buy one for the room that you spend the majority of your time in. Once you decide on the room, buy a unit that is big enough for that room. Some vacuum cleaners use HEPA filters too.

Are HEPA filters long-lasting?

These filters last two to three years if used for residential purposes. When used for commercial purposes on a regular or daily basis, they should be checked every six months. If you notice that they are heavily soiled, then replace them immediately; else, change it every year.

Also read,

Best Water Purifiers in India
Best Ceiling Fans in India
Best Air Coolers in India

Can we clean the HEPA filters ourselves?

Experts say that it is best to replace them rather than clean. If the filter is labelled “washable,” then you can try cleaning it. You will need extreme care in doing so. It might damage the mesh of fibers. There is no defined procedure for washable HEPA filters. There are no studies to prove how well these filters will work once washed.


HEPA filters were first used in world war II. When placed inside the gas mask, they were highly efficient in capturing chemical smoke. They were evolved in the 1940s for the Manhattan Project to prevent the spread of airborne radioactive pollutants. Over the years, the filters have become more advanced as the demand for better air quality has grown.

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