Here’s why: When infected people talk, sing, cough or even breathe, they release the virus into the air in a range of particle sizes. Although the large respiratory droplets fall quickly, the smaller aerosols can remain in the air for 30 minutes or longer until removed through ventilation or captured by an air-purification system.
The two experts are not advising that you rely on purifiers to entertain company. “Having people into your home for a meal or perhaps staying several days is a big concern as the holidays approach,” Corsi says. “Some may have been exposed; others don’t even know that they are infected.” They emphasize that people should not cease wearing a mask or washing their hands just because they have a purifier. “Don’t let your guard down. A purifier may lower the level of particles in the air, but it doesn’t eliminate the risk,” Corsi says.
Should you decide to buy a purifier, you’ll need to determine the best size for your space. For those mathematically challenged, like myself, try the Harvard-CU Boulder Portable Air Cleaner Calculator. Though designed for schools, it works for any measurable space. (You have to download the tool to your computer, so you can input your own data into the yellow boxes.)
The calculator will ask you for your room size, ceiling height and ventilation situation. The other important number is the Clean Air Delivery Rate (CADR). This number tells you how much air passes through your chosen purifier and its efficiency. The higher the CADR, the more air changes per hour. Your goal is three to five total air changes per hour.
You can find the CADR in the purifier’s specifications or on its packaging. If you can’t, you may want to bypass that brand. Look for a CADR of 250 to 300 or higher, Corsi says. If you see multiple numbers, use the dust rating.
A quality HEPA air purifier will cost between $200 and $300. Stick to the basics. You don’t need add-ons such as UV or ionization. There’s no benefit, and they will probably make the purifier more expensive or may introduce a secondary harm such as ozone, Allen says. Some models are quieter or come with timers and remote controls, but that’s just personal preference.
For maximum benefit, situate your purifier in the center of the room, at least three feet away from walls and corners and elevated on a stool or table. You also need to set it on the highest setting, and, yes, it will probably be somewhat noisy.