Interest peaked after New York Governor Andrew Cuomo announced last week that malls in his state wouldn’t be allowed to reopen until they installed HEPA (short for "high efficiency particulate air" ) air filters. But before you run out and buy one of the pricey home filtration systems, know that it’s not a failsafe way to prevent SARS-CoV-2, says Jill Grimes , MD, a family physician in Texas. It shouldn’t be your first — and certainly not your only — line of defense. No filter will be a substitute for wearing a mask and social distancing , the two most effective ways we know of to combat catching the disease. “You can think of an air purifier as an extra layer of protection, but it won't make you bulletproof,” Grimes says. “You might have a HEPA filter in your office, but that doesn’t mean you don’t wear a face covering.”