Symbol 3617 from ISO 7000 - Title/Meaning: Gas, lighter or heavier than air 
Function/description: To identify that the gas container or system (e.g. in a vehicle) contains gas that becomes lighter or heavier than air when released
Own work using: iso.org/obp/graphics/grs/f0aada75-b674-4324-a2db-32feeaa41194 200.png
Vectorization:  Mrmw