"An N95 is more protective because it has a better face seal in general than a KN95 or a KF94," explains Aaron Collins, a mechanical engineer with a background in aerosols science. He's also known as the Mask Nerd because he's been testing hundreds of masks over the last year and a half. (You can explore a master spreadsheet of his results here.)

https://docs.google.com/spreadsheets/d/1M0mdNLpTWEGcluK6hh5LjjcFixwmOG853Ff45d3O-L0/edit?usp=sharing //

N95s are strapped to your head with a headband, which gives them a snug fit – and with masks, a tight fit is key to better protection. In its new guidance, the CDC notes that N95s and other NIOSH-approved respirators are the most protective options.

By contrast, both KF94s and KN95s attach with ear loops, which many people find more comfortable but don't seal quite as tightly to your face. //

N95s are made to U.S. government standards put out by the National Institute for Occupational Safety and Health and are rigorously tested, so they're a reliable choice. KF94 is a South Korean standard, and they're regulated by the Korean government. "Every [KF94] I've tested so far has been extremely high performing," Collins says.

KN95 is a Chinese respirator standard, but these respirators aren't strictly regulated by the Chinese government, according to both Collins and Anne Miller of Project N95, a nonprofit organization that connects consumers with legitimate masks and other PPE. While you can find some good KN95s (the ones made by Powecom have done well in tests), low-quality or outright fake KN95s have been a problem throughout the pandemic. //

Can I re-use an N95 or other respirator?
Yes, though Miller advises following the "brown bag decontamination method." Basically, if you need to wear a respirator all day for your job, at the end of the day, put it in a brown paper bag or hang it up in a cool, dry place. The idea is to let it rest for five days so any viral particles trapped on it can die off. Label the bags Monday mask, Tuesday mask, etc. The CDC advises reusing an N95 respirator no more than five times. (Health workers shouldn't reuse them.) Using this guideline, a rotation of just five respirators could last you 25 days, Miller notes.

What if you only don an N95 for a quick trip to the store every now and then? Then think about your respirator's total lifespan being about 40 hours of use, Miller advises – the equivalent of five eight-hour days. If the respirator is dirty or getting harder to breathe through, or the straps have gotten stretched out, it's time to toss it out.