Health

A Basic Introduction to Filters used in Powered Air purifying respirators

When you are shopping for powered air purifying respirators, the very first thing you are advised to check is the type of filter used in the PAPR respirator. The term HEPA is often thrown around when it comes to filters for PAPR. If you don’t know even the basics of HEPA filters, this article is for you. HEPA filtration is an important technology used in powered air purifying respirator and other equipment used for air purification.

You need to understand HEPA filters before you order powered air purifying respirators.

HEPA (High Efficiency Particulate Air) Filter

All types of filters for PAPR and other equipment used for respiratory protection come with some claims and benefits. However, HEPA filters actually deliver what they promise. Each filter gets tested and approved to qualify as a HEPA filter. If a filter fails to trap 99.97% of particulates 0.3 microns or larger, it is not a HEPA filter. High efficiency particulate air filters can also trap particles smaller than 0.3 microns. 0.3 microns is simply a threshold.

What is Micron

The size of particles ranges from ultra-microscopic to the size that you can see with your eyes. One micron is one-millionth of a meter. Microns are used to measure particles. Human eyes need specific equipment to see anything less than 10 microns. See the table below:

Pure Oxygen 0.0005 microns
Car Emissions 1 – 150 microns
Bacteria 0.3 – 60 microns
Mould 3 – 12 microns
Spores 3 – 40 microns

How Does a High Efficiency Particulate Air (HEPA) Filter Work?

A HEPA filter consists of a complex web of fibres that traps air contaminants. Depending on the particle size, a filter achieves this in the following four ways:

Sieving

Interception

Diffusion

Inertial Impaction

Sieving and inertial impaction are used to trap larger contaminants. Particles get trapped either when they attempt to travel through the fibres or collide with the fibres. Interception is used to trap medium-sized particles travelling through the filter. Smaller particles dissipate while travelling through the filter. These particles get trapped when they collide with the fibre.

Keep in mind that all HEPA filters are not the same. HEPA filters can have different composition and utilization.

In some HEPA filters, the air passing through an ionizer puts a negative electrostatic charge on the incoming particles. These filters have a gradient composition of synthetic fibres. As the air reaches the HEPA filter, these charged particles get trapped in the fibre.

Some HEPA filters do not only trap but also reduce contaminants. This prevents allergen build up and viruses and bacterial growth on the filter. This improves the overall efficiency of filters. Other filters use nanofibres that can filter particles smaller than 0.003 microns.

HEPA is one of the different air purifier technologies such as ozone, ionizing, activated carbon, and UV technology. Some air purifiers use these technologies in conjunction and others use only one technology. When you are considering air purifier technology, you must be aware of your expectations.

There is no guesswork involved when you are buying powered air purifying respirators with high efficiency particulate air filters. Shop from an online supplier selling tested and approved products.

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