Although the CDC states that the main threat of infection is thought to be spread through close person-to-person contact , there's still a reported air quality improvement case to be made for protection against airborne transmission starting with a building's or home's ventilation. According to a CNN article that consulted with Harvard environmental health researcher Joseph Gardner Allen, and, in lieu of a statement made by Governor Cuomo: properly ventilated buildings with high-efficiency air filtration systems can be an initial line of defense against the coronavirus . Which brings us to HEPA: If you've considered purchasing an air purifier or already own one, then you may be familiar with this four-letter filter but may not know what it actually entails. HEPA ( which stands for "high efficiency particulate air" ) filters are rated at the top of their class for their ability to trap tiny particles in the air (around at least 99.97%, theoretically). But, it's this star quality that also makes it difficult (and expensive) to install HEPA filters on larger multi-room scales (e.g. as part of an entire home's ventilation system). This is why we so often see these top-performing filters employed inside smaller, room-by-room air purifier models.