Make no mistake about it, the climate control system for the Model X is superior to anything available from any other manufacturer and will do an excellent job of protecting its occupants from harmful elements in the atmosphere. Tesla describes the system this way, “The biodefense button is designed to allow clean medical-grade air into the cabin and keep contaminated air out. When deployed, it pushes the system into full fresh mode, pulling all HVAC air through the HEPA filter. The fan goes to max speed 11, pulling in enough air to slightly pressurize the cabin, keeping other air from entering Model X.”

But a few people with actual bioweapons experience quibble with the Tesla Bioweapons Defense Mode claims. The issue is not whether the system works, but whether its claims regarding viruses are accurate.

Colonel Randall Larsen, retired from the U.S. Air Force and now the director of the Institute for Homeland Security, tells Gizmodo that he is actually a Tesla fan. “I’m actually building a new house, and I had them put an electrical charger in the garage, just in case I buy a Tesla,” he says. But when told about the Tesla Model X “bioweapon defense mode” he laughed out loud and asked, “So, is Musk actually advertising this?”

To be considered a real HEPA filter, an air filter has to remove 99.97% of 0.3 micrometer particles from the air. That’s fine enough to catch bacteria like anthrax. It will also stop the plague and most other bacteria, as well as most pollen, dust, and fungal spores. “Now, if you’re worried about bacterial agents like anthrax or plague, a good filtering system would probably protect you,” says Larsen.

But viruses are much smaller than bacteria, which means they’re harder to filter out of the air. “Well, 0.3 micrometer won’t hold back viruses. It will hold back most bacteria, but it won’t hold back viruses. So, if you believe that all bio-terrorist agents are bacteria, then you’ll get an increment of protection,” said Michael J. Buchmeier, deputy director of the Pacific Southwest Regional Center for Biodefense and Emerging Diseases at the University of California, Irvine.

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The influenza A virus is only 120 nanometers wide, so it can pass through even a 0.2 micrometer HEPA filter without a problem. “It’s a statistical game that we play,” said Buchmeier. “Any filter like that is going to be efficient to a degree but it’s not necessarily 100% efficient.”

Larsen and Buchmeier also point out that, by the time the passengers realize there has been a bioweapons attack, it will probably be too late to take protective action. “The key problem with the bio is knowing when it’s been released,” Buchmeier says. “You know, it’s not like there’s a big bang or something. It’s a pretty extravagant long shot anyway, you know, the idea that you’re going to be forewarned enough to implement this filter in time to prevent any exposure.”

None of which should take away from how good the Model X climate control system is at protecting its passengers. It can filter out allergens like ragweed and cedar pollen, fungal spores like the ones that cause Valley Fever, and irritants like smoke and dust. It could also filter out unpleasant roadside odor. “There are a lot of reasons why you would put a filter like that in, and only one of them is bioterrorism,” says Buchmeier.