Tesla just unveiled its latest electric supercar, the Model X. Among other mind-blowing features, it has something built in called "bioweapon defense mode."
It's one of three modes on the Model X's air conditioner: you can circulate air from outside, recirculate the air inside, or punch the button for "bioweapon defense mode." This causes positive pressure to increase in the cabin to keep outside particles out, and engages a HEPA filtering system.
HEPA filters are fine enough to stop most bacteria, like anthrax and the plague, as well as dust and pollen. But viruses are smaller than bacteria, and could likely get through the filters. Gizmodo talked with Michael J. Buchmeier, deputy director of the Pacific Southwest Regional Center for Biodefense and Emerging Diseases at the University of California, Irvine, and he allowed that smallpox and influenza could get through the HEPA filters.
So while your air will be safer in the Model X with the bioweapon defense mode deployed, it's not a 100% guarantee. And, more importantly, you'd have to know there was a biological attack happening, when in reality those aren't usually detected until it's too late. In the end, bioweapon defense mode will get you some nice clean air, but it's probably not going to save you if there's a real bioweapon attack.