Tesla’s bioweapon defense mode may have more real world applications than providing peace of mind about possible zombie attacks. CEO Elon Musk shared an inspiring story on Friday from Twitter user Olof Tenghoff, who claims his daughter was able to sit in his Model S without suffering from asthma attacks.

The mode first debuted on the Model X in September 2015 as part of the $6,000 premium upgrades package, before joining the Model S in 2016. At the feature’s launch, Musk claimed that with a push of a button, the air filtration system kicks into overdrive and filters viruses 800 times stronger than normal. Musk claimed on Friday that when the mode is activated, the inside of the car has the air quality of a hospital operating room, which means it should protect “against even a weaponized virus.” In the case of Tenghoff, it’s enabled his daughter to ride in the car with much cleaner air than otherwise, mitigating her asthma attacks.

Musk noted that beyond the bioweapon-focused mode, the two cars “also have an acid gas filter, an alkaline gas filter & a carbon monoxide detector that autoswitches car to [recirculate] mode,” which is able to filter “bacteria, viruses, spores, pollen & particulate of almost any kind.” Unfortunately, the filters are too big to fit on the cheaper Model 3 sedan — just one of the many extras customers receive if choosing the more expensive Model S.

Whether the feature will end up saving a driver from an actual bioweapon attack is up for debate, mostly because attacks can take days or weeks to reveal themselves. Michael J. Buchmeier, deputy director of the Pacific Southwest Regional Center for Biodefense and Emerging Diseases at the University of California, Irvine, told Gizmodo after the feature’s announcement that “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.”

While most media focus is on the Model 3 that’s gradually rolling out to customers with a $1,000 reservation, Tesla is expected to provide further updates on the status of the Model S and Model X at the company’s next quarterly earnings call, expected to take place in August.

It’s not the only car Tesla is currently working on — the second-generation Roadster is also expected to hit the road in two years’ time.