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.