- Fixes breathing not producing CO2. This applied to humans (untested for other races, but probably the same)
N2 buildup fix attempt. Putting this into separate commit in case it's not wanted.

- Right now, air consists of 20% O2 80% N2 (approx.). Breathing takes O2 and turns it into CO2. CO2 gets scrubbed. Pressure drops, vents refill with air which again contains 80% N2 20% O2.
- This means that only 20% of breathed-out oxygen is replenished. Rest is replaced by N2. In large areas, such as Bar, with many mobs this can eventually lead to dangerous atmosphere status.
- This fix, while OOCly slightly unrealistic handles this issue by turning both O2 and N2 into CO2. Tested in CE's office with 5 human mobs without active scrubbers. Air lasts for 2~ hrs. Larger areas of course last significantly longer.
Revert "N2 buildup fix attempt. Putting this into separate commit in case it's not wanted."

This reverts commit e8a7b58affde1dd75e8923802559e18f0e8e454b.
Merge pull request #5983 from atlantiscze/co2-breath-fix

CO2 Breath fix