HEPA stands for “High-Efficiency Particulate Air”. HEPA filters are air filters that capture airborne particles like pollen, dirt, dust, moisture, bacteria, virus, and more.
The HEPA filters must satisfy a certain level of efficiency of air filters. It requires a standard air filter that can capture 99.97% of any airborne particles of 0.3 microns. This standard level of 99.97 % of 0.3-micron particles is defined by ASME (American Society of Mechanical Engineers) and the United States Department of Energy (DOE).
The Hepa Filters are made of randomly arranged fibers. These fibers are attached to each other as a mat and create a narrow path through which air can pass. Most of the best air purifiers use HEPA filters to refresh indoor air.
What type of particles do HEPA filters capture?
Hepa Filters are usually used to remove pollutants and airborne particles. These filters can capture pollen, dirt, dust, moisture, bacteria, virus, fog or mist, dust, forest exudates, geyser steam, smoke, steam from a kettle, sprayed pesticides, and more.
Usually, HEPA filters do not trap gasses and odors. Activated Carbon filters are used to trap gases and odor molecules. Sometimes HEPA filters are added with activated Carbon filters to increase efficiency and trap odors, cooking smell, chemical smells, and gas molecules.
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Working of HEPA Filters
Hepa filters are bundles of fibers that are randomly arranged as a mat. They are made in such as way that air can only flow between these narrowly arranged fibers. They create a narrow path to pass the air and block the particles.
The space between filter fibers is more than 0.3 microns, still, it can trap particles lesser than 0.3 microns. It is because these fibers are arranged randomly so the particles collide and stick with the fiber and then get stopped.
These fibers physically trap the particles passing through them while following below listed three mechanisms:
Diffusion – The small particles below 0.1 microns follow this mechanism as they collided with filter media fibers. This is the best possible when the airflow speed is lower.
Interception – This process captures mid-size particles, as the particles adhere between the side of fibers.
Impaction – This mechanism is for large-size particles, and these large-size particles directly impact fibers and get stopped.
Uses of HEPA filters
HEPA filters are used in many applications.
This filter is widely used in the medical industry to stop the spread of airborne bacterial and viral organisms. So, it can stop infections due to airborne bacterial and viral organisms. In the medical industry, the Hepa filtration technique is used with UV radiation technique to kill the trapped viruses and bacteria.
It is used in air purifiers to refresh breathing air. This filter is also good for reducing allergies and more. It traps air pollutants available in the room and makes air refresh to inhale.
Vacuum cleaners also use HEPA filters. This is good for allergic people. Ventilation and air conditioning also use HEPA filters in their filtration techniques to trap pollutants.