Ventilation Required For Gyms ?

The situation is this.
A large shed in a suburban area that had been used by someone in a steel/Al fabrication business was turned into a local gym. The overall size is around 25′ deep by 30′ long.
Usual modern gym gear, weights machines, run treadmills, etc plus dumbbell zones.
No showers, pools or anything else.
When there’s a good crowd in the gym, the air is awful stuffy and the only inlet or outlet is the normal sized entrance door at one end which opens onto a short corridor that leads to the gym area. (Jax and office rooms off that corridor.)
The roof is the typical old timber couples with corrugated iron upon them. About 15′ high at the ridge.
There may be an odd old perspex sheet among the corrugated iron to let in natural light. But the gym is lit by electric light all day.
I see no fans or baffles to guide any air that might eventually come in via the main door — assuming that the main door was left open — which it often isn’t.

My – unprofessional – view is that such an establishment would require better ventilation arrangements than are there. People go to a gym to exercise, not to intensively inhale other people’s expulsions.

But are there any regulatory planning requirements to have proper ventilation/air-changing in this type of public facility ?