Tesla says its HEPA air filtration system, which comes standard in the Model X and the new version of the Model S, not only scrubs the air inside the vehicle—it also reduces pollution directly outside the car as well.
The company placed a Model X SUV in a large bubble with extreme levels of pollution, approximately 8,200% above the EPA’s “good” air quality index limit of 12 micrograms per cubic meter of air of fine particulate matter. Testers then closed the doors and hit the “bioweapon defense mode” button, a special setting activating a medical-grade level of the filter.
In less than two minutes, the HEPA filtration system had scrubbed the air in Model X, bringing pollution levels down to levels so low that they were undetectable by the company’s instruments, according to Tesla. Testers were able to remove their gas masks and breathe fresh air while sitting inside a bubble of pollution, the company says.
Get Data Sheet, Fortune’s technology newsletter.
The filtration system, which has three carbon absorption layers strip the air of pollen, bacteria, and pollution, then began to vacuum the air outside the car as well, reducing fine particulate pollution levels by 40%, the company explains in a blog post. Tesla posits the results prove “the 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.” The company also provided a graph, below, charting out the progress.
Fine particulate matter, or PM 2.5, is a mix of tiny particles and liquid droplets that are made up from acids, organic chemicals, metals, and soil, or dust particles. This is the stuff reducing visibility and causing the air to appear hazy when levels are elevated. They’re small enough to become embedded in the lungs, causing a slew of health problems, including aggravated asthma, irregular heartbeat, and premature death in people with heart or lung disease. Average annual PM 2.5 levels reach 56 micrograms per cubic meter of air (µg/m3) in Beijing, 25 µg/m3 in Mexico City, and 20 µg/m3 in Los Angeles.
Bioweapons experts have cast doubts on the capability of the filter. This test—which it should be noted was conducted by Tesla—might be an attempt to silence critics. A filter with this kind of capability would be an attractive feature for anyone who commutes every day in heavily polluted areas like China, a market Tesla is trying to reach. The company might be anxious to provide evidence that it really does work as it claims.
The car maker also says it tested the filtration system outside the lab in areas known for poor air quality, such as California freeways during rush hour, landfills, and cow pastures in the central valley of California as well as major cities in China.
Tesla notes in the blog post that it was inspired by the air filtration systems used in hospitals, clean rooms, and the space industry. It turns out that the early seeds of the idea were planted by Google co-founder Larry Page. Tesla CEO Elon Musk sent out a tweet Monday giving Page credit for initially educating him about the health benefits of filtering particulates.
Filtering particulates from air makes a significant & measurable diff to health. Wd like to credit Larry Page with turning me on to this.
— Elon Musk (@elonmusk) May 2, 2016
Another interesting details revealed by Tesla: it isn’t finished with the air filter. The company says it is trying to improve the defenses in the primary and secondary filters, which are replaceable.
