About HEPA Filters: -
1. HEPA stands for High Efficiency Particulate Air, is a mechanical air filter.
2. It filters out smaller particles like dust & dirt particles of size 0.3-micron dia.
3. It works by forcing air through a fine mesh that traps harmful particles such as pollen, pet dander, dust mites, and tobacco smoke.
4. Because of this risk of nosocomial spread of SARS CoV-2 reduces.
5. Like influenza, COVID-19 is transmitted
by respiratory droplets, which can linger in
A patient who asks for a glass of water in a
crowded hospital hallway can generate
thousands of droplets per second. What happens to the person without a mask who steps into that air space?
6. Modifying existing HVAC systems, which hospitals have been optimizing for decades to prevent airborne transmission of other pathogens, doesn’t make sense to Mr. McDavid. If anything, some facilities, such as the Johns Hopkins Hospital, in Baltimore, are adding more of what works, such as HEPA filters and negative-pressure rooms to create more space to isolate COVID-19 patients.
7. According to NIOSH, HEPA
traps 99.97% dust particle 0.3-micron dia.
8. Simplest filter is the sieve.
9. To catch smaller
dust & dirt very fine filter or several filters on top one another is
10. Vacuum cleaner clogged contaminants very quickly but it required more power and energy so it is costlier.
11. Filter works like sieve to stop large particles like dirt, dust, hair.
12. There is concertina inside the filter which is the folded paper designed to trap small particles. Paper is the mat of very dense glass fiber.
13. Also it uses 3 different ways to filter out dust particles. At high speed air particles trapped as they snatch directly into the fibres, other clogged on fibre. Air at lower speed contains dust particles which wander anywhere and may stick to the fibre. This motion is called as Brownian motion.
14. These 3 mechanism allow HEPA to catch smaller & larger particle size than certain target size.