It’s the thinking person’s altitude training!

Off-gassing toxins for long lasting training benefits free of charge! Feel the burn!

Depends on the exercises you do. An outdoor gym is feasible depending on climate, air pollution, and what's available in parks. (Or simply cycling/jogging outside)

Home gyms can cover part of it. You can do a lot with a chinup bar, bodyweight exercises, powerblock dumbell sets.

I'm actually in a city too cold to go without a gym year round, and I do barbells so I can't do those at home (space too small). But, mentioning the options above for those who don't have the same constraints.

Start sharing it with your fellow gym members and collectively demand that management make some changes to improve air quality. Crowdsource some testing devices to prove your point if necessary, now that you have an idea of which points you have to prove.

Go during off hours when there are less people disturbing all the plastics and breathing the precious oxygen.

Just more pleasant in general as well.