My gym is in a converted warehouse. Probably 30' ceiling at least, so it's mostly open air. Lots of fans and HVAC so the air is constantly moving. It was closed from March - June of 2020. Reopened in late June with masking and social distancing as per local rules. There was an exception to the masking rule "while exercising" so basically nobody wore a mask in the gym. I returned to my every other day habit, my workout takes about 90 minutes and then I sit in the sauna for 20 minutes and then shower.

I'm not aware of any local cases linked specifically to gyms, so it seemed to work out fine.

> If anything I'd expect gyms to be better ventilated than offices or supermarkets

I certainly wouldn't be at all surprised if gyms ended up being safer than offices and supermarkets. Offices in particular (where one typically spends hours in the same room) seem pretty unsafe to me.