Symbol 1320 from ISO 7000 - Title/Meaning: Pressurized, open slowly 
Function/description: When used as an indicator alerts the operator that a piece of equipment is under pressure and to open slowly.
Own work using: iso.org/obp/graphics/grs/13d50535-082e-4387-be93-46eeedba2055 200.png
Vectorization:  Mrmw