Comment by Dylan16807
1 day ago
Of course air is mostly nitrogen. But if you replace 10% of the air with pure nitrogen you go into OSHA-angering levels of oxygen depletion, and if you replace 25-30% you get into serious danger.
Not easily achieved in a tunnel, but much more easily achieved in a garage.
10% of the air replaced with pure nitrogen would be 0.8 * 0.9 + 1.0 * 0.1 = 82% nitrogen, 18% oxygen. That's perfectly safe for brief exposure, which is all it would be before you return to ambient levels.
To create a dangerous scenario you've gotta do something like somehow gas out your entire tank in a garage and then just stand around for a while breathing it in. Kind of an improbable scenario unless somebody is trying a really weird suicide attempt.
The bigger tank apparently holds 250kg of air. That's about 200 cubic meters. A two car garage is likely less than 100 cubic meters.
You wouldn't need to dump nearly an entire tank of nitrogen to reach levels that are immediately dangerous. And oxygen deprivation makes you stupid well before it makes you pass out, with no "lack of air" panic since that is based on CO2 levels, so even when it would be survivable for a couple minutes you might not even think to escape.