When discharging industrial gas into the indoor environment in high altitude astronomy, we never wore breathing respirators that fed us oxygenated air at above the legally required 19.5% oxygen levels.
Steven Magee
air, altitude, astrobiology, astronomer, astronomical, astronomy, astrophysics, astrosociobiology, breathing, discharging, environment, fed, gas, high, indoor, industrial, legally, levels, liquid, osha, oxygen, oxygenated, respirators