Tesla’s “Bioweapon Defense Mode” Is as Effective As…A 2010 Mazda?

Tesla rolled out its “bioweapon defense mode” to lots of fanfare and media attention. Tesla went big:

“Bioweapon Defense Mode is not a marketing statement, it is real. You can literally survive a military grade bio attack by sitting in your car.”


Elon’s telling the truth, but not the whole truth. Tests I’ve done show that most cars already have a “bioweapon defense mode”: it’s called an air filter.

Like the true nerd that I am, I emailed Tesla and offered up my data.

I’m not surprised they didn’t respond, but it makes me feel absolved about doing a take-down on their press release.

Tesla Bioweapon Defense Mode vs. Ohad’s 2010 Mazda

Tesla released a test of how fast its bioweapon defense mode could reduce tiny particles. They even put the Tesla in a huge plastic bubble to do the test. 

And the results were impressive. Particulate dropped dramatically in less than 5 minutes.

But when I saw the graph, it reminded me of tests I did with the help of Smart Air aficionado Ohad in Israel. We were wondering air is any better inside cars, so Ohad used a Dylos laser particle counter to track what happened to particulate levels after he turned on the AC in his 2010 Mazda 3.

Ohad did nothing special to his Mazda. He put in no special filter. The filter was just whatever was already in the car. He didn’t even put in a new one. Here’s what the tests in Ohad’s Mazda looked like.

Since the Tesla graph reminded me so much of the Mazda data, I lined up the data sets to the same baseline particle level and put the graphs on top of each other. The red line is the Tesla data; the blueline is Ohad’s Mazda data. 

Ohad’s Mazda was almost identically strong—just about 30 seconds slower than the Tesla bioweapon defense mode. You can read more about the shockingly awesome car air systems in this test. Based on this data, I guess all car companies should start advertising their vehicles as bioweapon defenses.

Well maybe there’s something special about Mazdas?

I’ve tested this in more cars by calling Ubers in Shanghai and Delhi and bringing along my particle counter, and the results were similar (see one test here). Cars have filters in them, not just Mazdas. Those filters are not HEPA filters, but the data shows they do a great job of reducing particulate. Just make sure to:

  1. Close your windows
  2. Run the air system on recirculate mode
  3. Get your filter replaced regularly
  4. Don’t waste money getting a special particulate purifier for your car (unless your car somehow doesn’t have a filter)

OK, OK, is there nothing special about the Tesla?

I should be fair to Tesla. Their system also includes an activated carbon filter. Regular cars don’t have that. 

Our car filters can remove particles, but carbon can reduce certain gases, like ozone. In my mind, that’s what could really set the Tesla bioweapon defense mode apart (and what I would have suggested that they advertise), but they’re presenting tests of the thing that our cars are already really good at. Maybe my message will get through, and they’ll publish tests of gas pollutants.

For now, I decided to lend my marketing skills to spice up the marketing for Ohad’s 2010 Mazda:

“[Ohad’s Mazda] is not a marketing statement, it is real. You can literally survive a military grade bio attack by sitting in [Ohad’s 2010 Mazda 3].”

And I couldn’t help but ask Smart Air Photoshop Wizard Yongxin to photoshop Elon Musk next to Ohad’s Mazda:

Open Data

As always, I made the raw data for the car filter tests open source, along with more details on the methodology for fellow data nerds.

Breathe safe!

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7 thoughts on “Tesla’s “Bioweapon Defense Mode” Is as Effective As…A 2010 Mazda?”

  1. Has any testing been done comparing the *passive* air filtration qualities of different cars – including Tesla’s HEPA?

    Personally I don’t want to drive around with max fan and recirculate, even just at the start of a journey and don’t imagine many people do. For this reason I do think Bio-Weapon Defence Mode is a bit of a gimmick.

    But with fresh air, quiet fan, maybe or maybe not using AC? I’d really like to find some data on that, and thus far I haven’t done. Tesla’s X/S filter is so enormous that it won’t even fit in the Model 3, so presumably it must be something special? I’d also love to know how effective the passive, laser-based auto-recirculate feature is on my i3.

  2. Next time just use µg/µm^3 instead of microns per cubic feet so it will be easier to compare with other results from other air quality sensors.

    How did you find out the same base line particle levels? How did you convert 5500 2.5 micron per .01 ft^3 to 300 pm 2.5 µg/m^3

  3. Re: CO2 level build-up claimed above.
    I have no conflicts or agenda other than I want us all to have clean air to breathe, but I have to question that CO2 level rises to dangerous levels with air on recirculate. I, and I imagine many others have drive hundreds of miles with the AC on high, recirculating, in my car, alone (2004 Honda Civic). If your statement is reflective of reality then why have I not passed out? Further, why are there not thousands of deaths annually from CO2 drowsiness caused crashes. Is it possible that all cars are pulling in some fresh air even on recirculate? Doesn’t Tesla’s own data suggest that there is in fact some pulling in of outside air?

    • Great thoughts Matthew, you’re right to point out that in conventional cars when switched to ‘recirculate’ mode for a long period of time, we are still able to survive! The answer may well be that like you said, all cars do still bring in at least some levels of outside air to negate any CO2 level build up. This is another great study; it will be good to see how recirculate mode affects CO2 levels and PM2.5 levels, and to find out if there is a balance of the two for a conventional car.

      Aside: Some people often think being trapped in a car may starve us of oxygen, but as is correctly pointed out here and above, it’s CO2 that is the big danger. We published an article on CO2 vs oxygen levels in our knowledge base, explaining this in more detail.

  4. Thomas, this is of course very interesting, and the advice to run the AC system on recirculate is always key. However, I think we might be slightly glossing over one key point with regard to usage patterns or benefits to the Tesla HEPA system. Car cabins can become like quasi gas chambers, and though the recirculate function allows the AC system – I believe in most cars, though my anecdotal testing experience is small – with a standard car AC filter, to dramatically cut the down particulate levels in a reasonably short period, the flip side is that CO2 rises fast and remains trapped. Not with the HEPA system. For a single occupant, with closed windows, CO2 rises over 1000ppm in a handful of minutes, and proceeds 2000, 3000 in relatively short order. At those levels, drowsiness/alertness, particularly on longer drives, can be an issue. If coupled with the notion that we should keep windows up and sealed for protection from the air, this can certainly exacerbate the problem. The Tesla system, which I do believe should become more of a standard (but that would incriminate auto manufacturers, basically stating their non-EV product is inherently toxic), allows us to keep CO2 vs oxygen levels within a very healthy/fresh spectrum. Was Tesla misleading? I don’t know. Most likely not. Car cabins are notoriously bad (witness a string of articles in the Guardian and on the BBC), when not running the AC fan hard on recirculate. Certainly the carbon element, coping with other gasses, has not been given enough play.

    • The cost of allowing outside air in (basically turning off recirculate mode in a standard car) is that VOC’s can enter. And wildfires emit VOC’s.

    • Although the 2 filters the Model X comes with has carbon, they shouldn’t be expected to last more than a few days. You can do the research on VOC removal with activated carbon, but it’s a bit murky. My understanding is that it takes lbs of activated carbon to remove sufficient VOC’s, and that they need to be replaced within weeks. The carbon impregnated media will not last more than a few days. Also, carbon doesn’t adsorb many VOC’s included NOx and formaldehyde very well.


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