To answer this question, we need to first answer if HEPA filters can capture particles as small as the coronavirus. The COVID-19 coronavirus measures 0.06 – 0.14 microns in diameter.
The definition of HEPA filters is that it must remove 99.97% of particles “greater than or equal to” 0.3 microns. What about smaller particles like the coronavirus and other viruses? Can HEPA filters capture these?
This exact question has led to years of confusion and false advertising claims about HEPA filters, and is now leading to more misinformation about whether HEPA filters can or cannot capture and remove the coronavirus that causes COVID-19.
Why HEPA filters are great at capturing the Coronavirus
The fact that HEPA filters are so good at removing tiny virus particles like the coronavirus is surprising as many of us believe that HEPA filters work like a net.
If a particle is smaller than the holes in the net, it gets through. Makes sense! However, it turns out that particles as small as the coronavirus, and other nano-particles get captured using a scientific phenomenon called diffusion.
Diffusion is surprisingly effective at capturing tiny virus-sized particles. According to NASA, HEPA filters capture “virtually 100% of particulates.”
Researchers at the University of Minnesota tested this question with weaker fiberglass furnace filters and higher-grade HEPA filters. In their test, they shot particles of silver from3 to 20 nanometersat the filters (that’s roughly 5 to 30 times smaller than coronavirus particles). The results showed that filters captured 99.99% of particles smaller than 5 nanometers. Bingo! HEPA filters are incredibly effective at capturing nanoparticles–even smaller than the coronavirus.
How long can the Coronavirus survive on HEPA filters?
As tests have only been carried out in lab conditions, it is a reasonable estimate that coronavirus on HEPA filters can survive for up to 48 hours to 72 hours. Read more...
AS good as HEPA filters are a capturing particles, they don't destroy the particles. This has lead to a lot of marketing hype with air purifying companies. The reality is that HEPA filters can re-release tiny amounts of particles back into the air but these amounts are much less than what normally passes through a 99.97% filter. Read more...
3 things to watch out for with COVID-19 and air purifiers
Air purifier positioning is important - Make sure every air purifier is positioned to blow air into a room’s open space rather than towards people
HEPA filters capture but don't “kill” viruses - However, research has shown that viruses typically become inactive within 48 hours on HEPA-like surfaces. When replacing or moving HEPA filters that may contain viruses, they should be handled with care.
Air purifiers don’t provide 100% protection against viruses - Air purifiers are one part of the ventilation strategy for long-range transmission, the other two being to open windows and a fresh air HVAC system with filtration. Hand-washing and sanitising surfaces will prevent fomite transmission and masks/social distancing will help prevent close-range transmission. Read more...
Source: Smart Air - full article and images