I also realized that even though the reasons behind my fears were valid, I would always feel miserable if I kept clingin

When buying an air purifier, avoid terms such as “HEPA-style” and similar — it could mean the filter inside the device is not as effective as a true HEPA filter. Some central ventilation filters are labelled with minimum-efficiency reporting value ratings (MERVs). But for portable air purifiers, HEPA filters are generally considered the gold standard. Also, if you have a purifier with a lower-quality filter, it’s unlikely you can modify it to accept a HEPA filter, says Joachim Curtius, PhD, an aerosol scientist at Goethe University Frankfurt.

If you’ve found a purifier with a HEPA filter and a decent CADR and ACH, you might still wonder whether it will really do the job of reducing airborne SARS-CoV-2, the virus that causes Covid-19. Some scientific studies offer confidence, however.

Once you’ve chosen a model, you then have to decide where to place it in a room. You should pick as central a position as possible — don’t stick it in a corner, says Jimenez. Curtius and his co-authors add in their preprint that the space around the device should be free of obstacles, so avoid placing it under a desk, for example.

Another study, in a German high school, evaluated the efficiency of portable air purifiers in a classroom used by 27 students and their teacher, all of whom were wearing masks. Class carried on as normal while the purifiers quietly hummed away and detectors monitored aerosol levels. The findings have been published as a preprint and are not yet peer-reviewed, but they back up the fact that HEPA filters decrease aerosols of a wide range of sizes in a relatively busy indoor space.

Although the study did not test specifically for the presence of SARS-CoV-2 in the air or filters post-experiment (just aerosols in general), it is “solid” evidence that HEPA filters work as intended, says Jose-Luis Jimenez, PhD, a professor of chemistry at the University of Colorado, Boulder. That’s important to confirm, he says, because some people have questioned whether HEPA filters really are effective against SARS-CoV-2.

“The fact that someone had to actually do that experiment and write the paper and make all that effort is just crazy,” he says. “And it’s just because of all these flat Earthers that are denying that filters work to remove the virus.”

Finally, there’s the clean air delivery rate (CADR), a rating on some purifiers that have been certified by the Association of Home Appliance Manufacturers (AHAM). The CADR defines how quickly a purifier can rid the air of specific types of particles, including dust and smoke — which may be roughly in the same size range as aerosols bearing SARS-CoV-2. These ratings don’t refer specifically to virus-cleaning capabilities, but experts suggest using a purifier with a tobacco smoke CADR that is roughly two thirds of the square footage of the room you want to use it in. So, a CADR of 200 in a room that is 300 sq ft, for instance, would indicate the device can be expected to efficiently remove bioaerosol-sized particles from the air.

One series of experiments in a room occupied by two Covid-19 patients at the University of Florida Health, described in the International Journal of Infectious Diseases, applied HEPA filters to air sampling devices. The researchers did this to ensure the devices were not gathering residual SARS-CoV-2 as they collected multiple samples over time. While they found SARS-CoV-2 RNA in many of their air samples, they didn’t find it when sampled air had passed through the HEPA filters — suggesting that they did indeed block the pathogen effectively.

To calculate this effect in a little more detail, after 15 minutes, a HEPA purifier with a CADR score of 300 would clear 99% of tobacco smoke particles from a room measuring 10 by 10 by 10 feet, according to a paper published in the journal Otolaryngology–Head and Neck Surgery.

Air Purifiers, Air Filters, and the Best DIY Hacks to Reduce the Coronavirus Risk How to clear the air in your home to protect against airborne Covid-19 transmissionelemental.medium.com

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to work out twice a day every single day in order to reap the benefits. In college, I typically did it three times per week (once to get a second run or cross-training session in, and twice to get a lift in). I will say that the lifting is key, even if you’re a runner. According to Runner’s World, strength training:

Purchasers will also want to consider the square footage of the space in which they want to use the purifiers — manufacturers generally advise what coverage you can expect for a given purifier, and you might need more than one. And another really important factor is the air changes per hour (ACH) rating, which tells you how frequently the purifier will cycle the air in its allotted space — five ACH means five changes per hour, and so on. Hospital rooms might have 20 or even 40 air changes per hour via commercial systems. For general use, six is a decent rule of thumb, though, suggests William Bahnfleth, PhD, a professor of architectural engineering at Penn State University. It means you can expect the air to be cleaned roughly every 10 minutes.

Giving your purifier the best chance to do its job is important, especially if you buy a relatively simple one that will work at a steady pace — no matter how many people are in the room. Some wall-mounted commercial models can, however, attempt to respond to an increased density of people within a space, including those made by Fellowes.

When buying your own purifier, you might want to consider the noise or decibel rating of a particular purifier. Check how loud it is when the fan is at maximum to ensure it won’t become a nuisance. Finally, some models also come with UV lights inside that are intended to kill biological pathogens. It’s an extra layer of protection, but a HEPA filter alone can be very effective.

That aside, there are few rules about how much proximity to potentially infectious people in a room matters. In a bar, for instance, is it better to have purifiers next to every table or in the middle of the space?