In practice, one would use energy recovery ventilation to exchange air with outside rather than a CO2 scrubber (not clear if you actually meant a scrubber).

The place to look is existing codes for ventilation. Exempli gratia: https://dos.ny.gov/system/files/documents/2020/09/2020-mcnys... (see PDF page 46). Regulations to enforce outside air being brought into human spaces already exist.

I have been in some office buildings in United States which had CO2 monitors in each meeting room, and the ventilation would engage to control CO2 below a set level. We would entertain ourselves by exhausting our lungs onto the sensors to trigger the ventilation system.

I should have said it more clearly, I just thought HN would take this stance regardless. If you tell an employer to ensure CO2 levels, and it shows an improvement in productivity, employers may think "Hmm. Let's improve this further!" and add O2 as well.

In terms of outside air, a lot of US cities I think would not benefit from that, all that much. Especially during certain parts of the day, with a lot of smog.

But regardless, all that entered my mind was "Once employers are required to add any form of scrubbing, and perhaps O2 injection, they'll over do it for optimal employee output." Regardless of whether it's helpful once the employee leaves the workplace.

I'm not against this, I'm just actually saying the regulation should be locally defined.