We have clip on sensors that measure N2, O2, methane, and CO2. If O2 drops below 18% you need to get out of the area immediately. It’ll give an irritatingly loud beep so others can hear. Nitrogen is the big killer though. Some workers will climb down the ladder into a N2 filled chamber only to suddenly fall off the ladder unconscious. Usually it doesn’t end well.
I’ve been advocating for nitrogen executions. It’s the most peaceful way to go. They can hold their breaths but once they gulp a lung full, they pass out and breathe automatically.
Not for very long ...