For short stays, disposable masks work fine - make sure they're rated n95 or better, and have two head straps.
Longer stays mean a lot of disposed masks, so you may want to invest in a replaceable filter version. There are three well-known brands seen in Beijing: Respro, TotoBobo, and infipure.
Respro is the most expensive, and you walk around looking like Hannibal Lechter. Not an easy fit (i,e, you're probably going to let in some outside air, and it slides down easily, putting pressure on your nose), but the most airflow if you're planning on running or biking. Filters claim to clean the air best. Definitely the most expensive, though designed to last longer than other filters, so they *say* it pans out after a year or so. Be warned, their 'customer service' is the pits.
TotoBobo is also not cheap, but the replacement filters are very affordable. They filter a bit less effectively than the Respro claims to (94% vs. 99%), but the mask is much easier to put on correctly (ensuring no outside air leaks in), it's compact and light, and you don't look like a movie villain. Gets a bit sweaty, but you can buy a version for heavy exertion which only covers the mouth.
Infipure is a new company with in-nostril filters. Odd feeling at first, but you get used to it. Useful if you have a small or medium sized nose. Mine is on the large end of things (not Pinocchio, but a healthy European-style nose), and it feels like air gets in around the edges. Definitely less obtrusive, and a brilliant idea.
Download a China Air Quality app, or use a trusted website (such as bjair.info ) to know when it's time to don the mask. And spend more time in the many parks here. Trees are your friends.
Good luck - it's a great city! over 5 years agoAnswered by Josh via WorldNomads.com