Comment by somenameforme
1 day ago
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.