Symbol 3615 from ISO 7000 - Title/Meaning: Gas, lighter than air 
Function/description: To identify that container or system (e.g. in a vehicle) contains gas that becomes lighter than air when released
Own work using: iso.org/obp/graphics/grs/26964396-a0f1-48b2-8bf5-886aabd086e4 200.png
Vectorization:  Mrmw