Although nitrogen gas makes up 78% of the atmosphere, we can't use it because nitrogen atoms must be broken apart first before. This nitrogen is very much packed and bonded with its atoms and would be useless to use since it can't be used for plants.
It's biohazard. Also if it's flammable the symbol will show a flame and if it's corrosive it'll show a image with a hand being dissolved or like a spot missing by a liquid being dropped from a tube
