The CO2 scrubber, would do the trick, I was thinking about hypocapnia but that probably isn't affected by inhaled CO2 but the rate at which you purge metabolic

The CO2 scrubber, would do the trick, I was thinking about hypocapnia but that probably isn't affected by inhaled CO2 but the rate at which you purge metabolic CO2. So not sure there is a downside to pushing it too far the other direction the way there is with O2. But I think a real scrubber based solution would be cost prohibitive and perhaps finicky and noisy compared to a ventilation based solution that would do 95% of the job.