As you’ve likely heard, the hot new virus everyone’s talking about and slowly descending into paranoia regarding is the Coronavirus (COVID-19), a new and rapidly-spreading virus that’s already caused over 2,700 deaths. Nobody wants this mess, so, naturally, its caused a resurgence of interest in air purification technology like the “Bioweapon Defense Mode” that’s optional on some Teslas. The question is, can such a system really help? Let’s find out.
While the name “Bioweapon Defense Mode” is an example of the usual Musk-type of overblown teen drama we’ve come to expect, it’s really just a large, capable filtration system.
The system uses a very large air filter, one that’s actually too large to fit in a Tesla Model 3—which is why the system is only available in Models S and X. So, once again, you have to spend real money if you’re into not dying of things, like pretty much everything in life.
The filter is said to be a HEPA filter, which stands for High-Efficiency Particulate Air, a standard that must remove, according to Department of Energy standards, 99.97 percent of particles with a diameter of 0.3 micrometers in size—as a reference, it’s said that an average person can see a dust mote that’s about 25 microns in size—so it’s a hell of a lot smaller than that. A human hair is about 70 microns in diameter, if that helps.
Under a microscope, a HEPA filter looks like this:
...a big random tangle of fibers. The air goes in, and the particles get trapped in the disorderly mesh, and as a result, never get to your lungs to cause trouble.
So, with this in mind, will a Tesla’s HEPA-grade air filtration system help keep you from getting COVID-19? Well, to figure that out, we need to know some numbers.
Specifically, we need to know how big the actual COVID-19 virus is. According to the New England Journal of Medicine, the virus ranges in size from 0.06 micrometers to 0.14 micrometers.
As you can tell with, you know, math, the COVID-19 virus is smaller than the lower end of what HEPA filters can catch at 0.3 micrometers, meaning it can likely pass through the mesh.
However, things aren’t all that simple. While yes, it’s smaller than the smallest HEPA-stopping particle size, companies that sell air purifiers (not surprisingly) suggest that a process called diffusion means that particles as small as COVID-19 viruses can be captured, and they cite studies that suggest that HEPA filters can capture nearly every particulate smaller than 0.005 micrometers.
Of course, it’s worth remembering that these people are trying to sell filters.
Tesla is also trying to sell you filters, especially if you buy them with a car wrapped around them, so it’s not a bad idea to keep that in mind when reading articles speculating on the Bioweapon Defense Mode’s effectiveness at preventing COVID-19 infection.
Also, it’s worth noting that a filter for outside air isn’t enough; the car would need to be completely sealed and maintaining a positive pressure, so all the incoming air is only taken in via the filtration system.
That means all the door seals have to be in perfect condition, and all the doors have to close and fit perfectly—something that’s not necessarily always been a strong point of Tesla, especially for the Model X’s complex Falcon doors.
To maintain positive pressure, the Bioweapon Defense Mode needs to be active, as it cranks the fan up to the max and attempts to keep positive pressure in the car. So, to be safest, the system would need to be on before you entered a potentially contaminated area.
Tesla’s air filtration system has certainly proved helpful in areas of wildfires and other highly polluted areas—but that’s dealing with much, much larger particles.
I think the big takeaway here is that the Tesla HEPA filtration system certainly can’t hurt—and in many cases, may actually prove quite helpful—but due to the small size of the virus, I don’t think we can say that it will absolutely protect you.
If you have it, and are in an area where there’s an outbreak, use it. Just think of it as another prudent precaution, but not a magic shield.
UPDATE: As many commenters have mentioned, the virus is normally transmitted via respiratory droplets, which are larger than the virus. It still may be possible for the virus to escape the droplets, but it’s far less likely. Again, the result is using such a system can’t hurt.