Whether you have been already using an air purifier or planning to use one, you must have heard the term ‘HEPA Filter’. Do you know what does it mean? How it is related to air purification? If not, you will get to know everything about it here in this post.
What does a HEPA Filter mean?
The term “HEPA” refers to “high-efficiency particulate air” (filter). Its use is quite prevalent in the air purification segment. This kind of filter was brought long back in the 1940s when experts were researching the atomic bomb. During the process, they developed a rug of randomly united fibers, prepared from either glass or synthetic objects. This synthetic material employed in the air filter is extremely like what’s applied in quick-dry T-shirts.
While fibreglass air filters are developed using glass, which includes alumina, silica, boron oxide, calcium oxide, sodium oxide, and magnesium oxide, they are not developed from these elements.
The best thing about HEPA filters is their exceptional efficiency in capturing differently sized particles. These particles may contain pollen, pet dander, allergens, germs, viruses, PM2.5, and more. If you are looking for the best air purifier for air pollution, you are more likely to get a unit with HEPA air filters.
With respect to the ISO or European rules, filters that are capable of removing ≥85% of particles but lesser than 99.95% are known as ‘EPA filters’ or ‘efficient particulate air filter’. These air filters do not meet the filtration specifications to be understood as a ‘HEPA air filter’.
On the other side, filters that go beyond the requirements of a ‘HEPA air filter’ and capture more than 99.99% of particles are popularly known as ‘ULPA filters’ or ‘ultra-low penetration air filter’.
How do HEPA filters work?
In regard to HEPA filters, it is necessary to differentiate among "True HEPA" filters and "HEPA Like," HEPA Style” or "HEPA Type" filters. Any filter that is able to eliminate 99.97% of particles of size bigger than 0.3 microns in order to become a HEPA filter. The Environmental Protection Agency (EPA), which has defined this standard, employs grades for HEPA filters developed by the US military, ranging from grade "A," the least effective HEPA filter to grade "E," the most effective filter.
HEPA filters are based on a specialized filtering mechanism that is very similar to a strainer, web, or sieve. However, it is far more complex and can capture even the minutest types of airborne particles.
The HEPA filter process is made up of four mechanisms: electrostatic attraction, interception, diffusion, and impaction. The first elements to be eliminated, like with other types of filters, are bigger and easy to capture. The bigger contaminants are captured during the initial stage followed by smaller and then finest particles. At the outset, such a filter contains differently sized particles.
Direct Impaction: Big size contaminants like dust, mould, or pollen, moves along an unrestricted route and comes into contact with a fibre, it sticks there only.
Sieving: A particle is carried between two fibres by the air stream, and due to the bigger sized particles get caught quickly.
Interception: Although airflow may easily reroute around fibres, due to inertia, particles stay around the edges of fibres and continue on their initial course.
Diffusion: Since finest particles travel more irregularly than bigger particles, they tend to collide with and adhere to fibres.
Should I buy the best HEPA air purifier which claims to remove 99.9% of airborne pollutants?
No, not always. Even a filter that claims to be able to capture 99.9% of big particles may not be able to perform by treating ultra-fine particles. The tiniest particles, which are known to be the toughest ones, are usually 0.3 microns in size. A filter that boasts its capacity to catch these particles is not telling you how well it traps these particles.
Cleaning HEPA filter
It is not recommended to clean HEPA filters using vacuum, water, or brushes as it is likely to damage them rather than doing any good.
Why HEPA is the best?
The international benchmark for particle filtration is led by HEPA. Ionisers tend to pose highest threat to humans as they contribute to air pollution. Since a majority of ionisers are unable to leave an impact, they (1) eliminate negative ions that adhere particles to the different surfaces in your house rather than actually eradicating them, (2) promote toxic ozone production, PM2.5, dangerous VOC Gases, and formaldehyde, and (3) generate harmful ozone, PM2.5, harmful VOC Gases, and formaldehyde.