Australia's Winter Paralympians will deal with air quality equivalent to the worst of the 2020 bush fires, and more than three times worse than concerning levels when they compete on Friday.
A telltale layer of smog descended on Yanqing and Zhangjiakou on Friday morning, and with it, came escalated concerns over air pollution and its effect on athletes.
Paralympics Australia has air filtration devices, left behind by the Australian Olympic Committee after the Winter Olympics, as part of an arrangement, throughout its accommodation across two athletes' villages.
But that won't help the athletes when they compete outside.
Para snowboard star Ben Tudhope is competing in the banked slalom at Zhangjiakou while para alpine skiiers Rae Anderson, Melissa Perrine and sighted guide Bobbi Kelly were in the giant slalom at Yanqing.
As of Friday morning, the air quality index (AQI) was 158 in Yanqing and 156 in Chongli, which is near Zhangjiakou Genting Snow Park.
"We talk about PM2.5, PM5 and PM10. They're the different sizes of particulate matter, being 2.5 microns, 5 microns and 10 microns," Paralympics Australia chief medical officer Dr Steve Reid told reporters.
"The bigger stuff gets filtered out through the nasal passages and upper airways and the really small stuff gets down into the small airways and causes things like broncho-constriction, airway inflammation and asthma, so it's the PM2.5 that we pay most attention to.
"Generally you'd really want to see that number as low as possible. Once it gets above 50 we start to be concerned about people performing outdoor exercise for long periods.
"For instance today around Yanqing the PM2.5 is around 130 and inside at our allotment with the air quality devices running through the units we've got it down to about 12. They make a massive difference in terms of the air the athletes breathe while in our accommodation.
"Certainly the PM2.5 of 130-140 would be something where if we were in Australia and having bush fires, those might be the times we see those numbers being reached and when we might be cancelling outdoor sporting events."
A couple of Australia's team members have asthma, which can be triggered by PM2.5 particles and their preventative medication was increased on Friday, but all athletes can be affected by poor air quality.
"If you're someone who doesn't normally get asthma, if the air is polluted enough then you can get nasty respiratory symptoms," Dr Reid said.
"Even if you don't develop respiratory symptoms, if you're exercising outdoors in a consistent fashion, just your performance gets blunted and you lose that performance edge."
While athletes need to practice and compete outdoors, throughout the Games, Australian team officials have limited athletes' recreation time outdoors in the village to days with clear air, with windows only open for ventilation on days of acceptable air quality.
"You can't take away from the fact that this is a sport that's practised outdoors and winter sports," Dr Reid said.
"What they have to do is just be efficient with their work. It's get out, do quality work, get back indoors again."
One source of relief for Australia's medics is there are no endurance athletes: biathletes or cross country skiiers in the team.
"If we were dealing with cross-country skiing on a day like today there would be much more concern," Dr Reid said.
"We're dealing with downhill athletes where they have a really intense effort over a couple of minutes.
"So very much a matter of go inspect the course, a couple of warm up runs, into the lounge, do your competition, back to the lounge, recover, get home again."
