Do Hepa Filters Remove Viruses

Air purifiers with HEPA filtration efficiently capture particles the size of (and far smaller than) the virus that causes COVID-xix, then the answer is yes. Furthermore, on Oct 5, 2020, the CDC changed its stance on how the virus is transmitted, and at present says information technology "tin can be spread by exposure to virus in small droplets and particles that can linger in the air for minutes to hours." In short, the CDC now acknowledges that the virus can spread via the air. That's a major adjustment of its prior position: that direct person-to-person contact, including via larger respiratory droplets that practise not travel far or linger in the air, was the principal vector, and that airborne (a.k.a. droplets) transmission was not a vector, period. Testify for airborne transmission has been mounting since the spring; to grab up on the course this inquiry has taken, read over University of Colorado-Boulder aerosols scientist Jose-Luis Jimenez's summary in Time. And it's worth noting that on September 18, the CDC published—and 3 days subsequently retracted, citing errors in an internal review procedure—a version of its guideline that stated flatly that inhalation of aerosolized respiratory aerosol "is thought to be the principal style the virus spreads."

Back to purifiers: The virus that causes COVID-xix is approximately 0.125 micron (125 nanometers) in diameter. Information technology falls squarely within the particle-size range that HEPA filters capture with extraordinary efficiency: 0.01 micron (10 nanometers) and above. Many media outlets have incorrectly stated that HEPA filters don't filter below 0.3 micron and therefore could not capture airborne coronaviruses. That's wrong. This NASA study of HEPA filtration is quite technical, just the graph on page 7 and the preceding paragraph practice a proficient job of explaining why HEPA filters are actually almost efficient—virtually 100% at 0.01 micron—at capturing ultrafine particles beneath the 0.three-micron HEPA exam standard.

a Coway air purifier on a rug, between a plant and a chair. — Photograph: Sarah Kobos

This means HEPA purifiers would efficiently capture viruses (and any aerosolized droplets of saliva and fungus that incorporate them) that are fatigued into their filters. In its advice on cleaning and disinfecting homes during the pandemic, the CDC recognizes as much: "When used properly, air purifiers can aid reduce airborne contaminants, including viruses, in a dwelling house or confined space." And in its guidance for wellness-care personnel, the CDC states that air from rooms where COVID-19 patients are beingness isolated "should be exhausted directly to the outside or be filtered through a high-efficiency particulate air (HEPA) filter straight before recirculation," and advises wellness-care workers to "consider the addition of portable solutions (due east.g., portable HEPA filtration units) to augment air quality in areas when permanent air-handling systems are not a feasible choice." Beyond this, medical facilities have employed HEPA filtration since the mail service–Earth War Ii era to capture airborne pathogens, and, during the COVID-19 pandemic, many school systems are using them to augment HVAC filters and natural (window) ventilation. (The New York City public school arrangement, the nation'due south largest, has purchased 30,000 equally of November 2020, for instance.)

What's less clear is whether a HEPA purifier would catch the virus prior to the point of inhalation. If you're sitting next to someone who has COVID-19, for case, an air purifier on the far side of the room is unlikely to protect you adequately. That raises another unanswered question about how constructive an air purifier tin be: What level of exposure to the virus causes an infection to brainstorm with? We are post-obit this topic closely, and we capeesh our readers' ongoing back up in helping us maintain accurate, current data.

Just even if you decide to apply an air purifier as a protective measure, we recommend that you as well continue to closely follow the CDC's other longstanding advice, including social distancing, wearing a confront covering outdoors, washing your hands frequently, and treating ofttimes touched surfaces with disinfectants. Every bit the CDC writes: "The best manner to prevent illness is to avoid being exposed to this virus."