I hope you don't have a gas water heater down there with you. I will admit that I'm not familiar with the use of flowing lasers. How is the oxygen being used? Cooling, creating the beam or the actual cutting process...... what? If anything I would at least vent the fumes outside via a squirrel cage blower. The normal air we breath is about 15% oxygen. When you start hitting 20% and above, first you become very alert and get a lot done to the point where you can't fall asleep. After that there is oxygen poisoning (death) and somewhere in-between, very rapid combustion rates. It's amazing how fast a cigarette will burn.