HEPA Filter

There are many different kinds of HEPA filters on the market. True HEPA filtration is considered as one of the best because its efficiency has been proven. They are used in the medical, pharmaceutical, and computer industries where a contamination free environment is required. Furthermore, they are also used in aerospace, NASA, biomedical, bioengineering, and surgical facilities. The reliability and efficiency of this typ of air filtration makes it a good choice when stringent air filtration is required for human health or for a clean room working environment.

The Definition

The letters HEPA stands for High Efficiency Particulate Arresting. Particulate arresting refers to being able to catch airborne particles as small as .3 microns in size. High efficiency refers to being able to capture and retain 99.97% of all particles passing through it.

Capturing and retaining 99.97% of all particles passing through it down to the size of .3 microns is the definition of a HEPA filter. Any filter that does not perform at this standard is, by definition, is not a HEPA filter. This means that for every 10,000 particles that pass through the filter .3 microns and larger, only 3 particles will get through.

For the definition of HEPA to be rated for the size .3 microns is significant. This size is considered to be the most difficult size to filter. Particles that are larger or smaller in size can be filtered with higher efficiency.

The Size of .3 Microns

How small is a micron and what size is one-third of a micron? To put this into perspective, the thickness of a human hair can range in size from 80 to 120 microns. It is difficult for the naked eye to see below 80 to 100 microns. On the lower end of the scale, .3 microns is 267 times smaller than the width of a thin hair. On the larger end of the scale, .3 microns is 400 times smaller than the width of a thick hair. Only a true HEPA filter can capture particles this small.

Particle Size

Particles that cause allergy symptoms can range in size from 1 to 500 microns. The size that cause the most allergic symptoms are in the range of 1 to 80 microns with particles under 50 microns in size being inhaled the most. The HEPA filter being able to catch particles down to .3 microns makes it an ideal filter for nasal allergy sufferers.

Particle sizes that are 10 microns and larger can be stopped by the nose hairs and the mucus in the nose. Particle sizes 4 to 10 microns can get past the nose and reach the bronchi tubes. Particle sizes smaller than 4 microns can reach into the lungs. With the HEPA filter being able to capture and retain particles as small as .3 microns, it is the first choice for doctors to recommend for people who have allergic rhinitis.

Air Changes per Hour

To clean the air that we breathe, the air must pass though a filter. The number of times that all the air in the room goes through the filter is an important variable in the effectiveness of the air cleaner. The number of times is express in an ACH rating. ACH stands for Air Changes per Hour. Filtering all the air in a given room four times (or more) an hour is highly recommended for people with allergies.

Air cleaners that have a HEPA filter usually come with a bigger, more powerful, and more expensive motor. For the HEPA filter to be able to filter out such small particles out of the air, the extra density of the filter creates air resistance. As a result, a more powerful motor is needed to have an effective rate of putting all the air in a given room through the filter. This principle also applies if it is put inside a vacuum. A more powerful motor is needed to have adequate cleaning power. As a result, they are more expensive.

Accessories

It is very common for a HEPA to come with a pre-filter. The pre-filter is very effective at catching the larger size particles. This will prevent the HEPA filter from clogging. The pre-filter will extend the life of the unit. Keeping the pre-filter clean will extend both the life of the pre-filter and the HEPA filter itself.

It is also very common for a charcoal filter to be part of the HEPA air cleaner. Even though .3 microns is small, it is not enough to take out tobacco smoke, gasses, fumes, and vapor. A charcoal filter allows the owner to enjoy the best of both worlds.

The HEPA air filter is so popular today because of the quality of job it does at catching and retaining small particles. Letting the allergens go once they are caught and sending them back into the air can sometimes be worse for the person who is has allergies. It is an ideal type of filter for those who require clean air. Look at one of your hairs and try to imagine a speck (or dot) that is 300 times smaller than the width of your hair. You can start to get an idea of how small of particles that the filter is collecting. This makes this type of filter perfect for those who need allergens cleaned out of the air.

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