But is the Santa Tony Soprano Ugly Christmas sweater marketing of purified air for your home just that, marketing? Or can it actually have a positive, and perceptible, impact on your health? Experts say yes and no. L. James Lo, Ph.D., a professor of architectural engineering at Drexel University who studies the health effects of indoor ventilation, says air purifiers can help in reducing the infectivity of aerosolized viruses. “An air purifier removes particles, and aerosolized viral droplets are very small particles,” says Dr. Lo. How much they can help depends on their CADR, or “clean air delivery rate,” meaning, as Dr. Lo explains, the equivalent of how much fresh air is being delivered into a space. “The downside here is that air purifiers can only be very effective in small spaces,” he adds. (This downside feels less negative when you consider the size of most New York City apartments.) Purvi Parikh, MD, an allergist with Allergy & Asthma Network, adds that while HEPA filters (the high-efficiency filters found in most of the fancier devices on the market) add a critical layer of protection, they are not foolproof. “Moreover, unless there’s a large amount of virus in the air and larger droplets, the purifier may not help as some viral particles may be too small for a HEPA filter, especially if aerosolized,” explains Dr. Parikh. She says that from a COVID standpoint, filtering the air in your home is certainly good, but less of a necessity than limiting visitors, wearing a mask, and frequently hand-washing. Both Dr. Lo and Dr. Parikh agree that opening windows and doors to circulate air can provide a risk reduction similar to most air-purification devices.