Before this year started most of you have probably never heard what a HEPA filter was. HEPA, which stands for high efficiency particulate air, is a very intensive system of fibers that filter out dust, bacteria, viruses, moisture and basically any contaminants that passes through it. So is it safe to fly in planes because of these filters?
Almost all commercial airlines right now use HEPA filters and in fact you'll have a hard time finding a commercial plane that doesn't have them. These HEPA filters were installed in planes long before Covid 19 even existed and has been a standard among airlines to maintain air quality in the cabin. So how does it work and how does it filter viruses that are extremely small?
Photo from ANA
How the HEPA filter works
Viruses are generally 20-30 nanometers or 0.03 microns in size, in other words super duper tiny. A HEPA filter is like a fishing net trying to catch fish, but these filters have big holes and can't catch viruses that small.
So how do these filters do it? When we sneeze or cough we actually coat the virus in saliva or mucus, and each virus isn't coated individually but they get clumped together and then coated with a layer of saliva or mucus. This makes the size of that clump of virus, mucus, and saliva into 1 micron meaning the HEPA filter is able to absorb it and filter it so that clean air comes out of the filter.
So it's safe right?
You could say that its pretty safe to fly now knowing HEPA filters are installed on airplanes, but here lies the problem. Cabin air gets refreshed and filtered every 2 to 3 minutes. So what if the person next to you sneezes and the air hasn't been refreshed or filtered yet? Theres nothing much you can really do when you think about it right?
According to several airlines including ANA, cabin air never stays stagnant. Cabin air is constantly flowing from the ceiling of the cabin to the floor where it goes to the HEPA filters. Why they say it takes 2 to 3 minutes for air to be filtered must mean the filtration process isn't as simple and instant as the air flowing through the filter. It probably takes time to filter the air before it gets sent back out into the air conditioning. What do you think? Think it's safe enough to fly?
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