(And I'm as big a Tesla fan as there is, but that's an objective fact from a QA perspective.)
But then again, testing against smog is something a group of engineers can do on their own. Testing against lethal and highly contagious airborn pathogens is hardly something you can just up and do in your ordinary automotive lab. Doubt they're prepared to handle that. Even getting your hands on the pathogens in the first place is difficult, let alone handling them in a safe manner for testing.
But if they're going to advertise this, that's what they need to do.
"Well, there's clearly no real way to get anything dangerous through here without the metal detectors picking it up, so no need to test our systems with any realistic threats."
* Aerosols are really the only effective way to deliver biological weapons. This holds even with person-to-person transmission; "airborne" transmission almost always means "infected person coughs, spreading aerosolized fluids that contain infectious bodies".
* Aerosol droplets smaller than .5 um don't land on parts of the lungs that can absorb them and are re-exhaled relatively harmlessly. Aerosol droplets smaller than .5 um also lose stability (evaporate, chemical changes, solar irradiation) too quickly to be useful.
"Realistic Threats" are, in this case, particles between .5 um and 5 um. There is zero difference between a droplet with and without an infectious payload. If you really wanted to you could do this test with some completely harmless organism like a household micrococcus strain, but it wouldn't demonstrate anything new. If there are no particles of that size coming through the filter, you are safe, in the same way that the plane would be safe if it took off with no people in it.
For the actual question: you probably leave the filter in place until it's clogged, at which point you replace it as normal except you're wearing a hazard suit. Those filters basically don't let anything go. However, note that the filter will be exactly as contaminated as anything else on the outside of the car is; a persistent weapon will have covered every surface in the attacked area with hazardous numbers of spores or similar, not just the filters. If it's not a persistent weapon - that is, it's designed to kill or incap everybody and then dissipate so your soldiers can walk in two days later and take over - then you just wait those two days.
And, possibly, illegal. I mean, it seems to me that asserting that the car provides a "bioweapons defense mode" (and, a fortiori, the marketing claim that "You can literally survive a military grade bio attack by sitting in your car") is clearly promoting the car with a claim that is a "machine...intended for use in the...prevention of disease, in man", and, as such, a medical device subject to premarket and postmarket regulatory control by the FDA: http://www.fda.gov/MedicalDevices/DeviceRegulationandGuidanc...
(2 minutes isn't that long to hold your breath for)
Unless you're being attacked with smog, this seems rather hyperbolic.
I can't imagine that two minutes breathing, say, aerosolized tweaked Spanish influenza, would be 'safe'. Maybe if you were in the car with the system running before the attack, though?