Symbol 1604 from ISO 7000 - Title/Meaning: Intake air Function/description: To identify intake air, for example combustion air for mixing with fuel in an internal combustion engine.
Additional information: 
Use to indicate air flow into or through a tube or pipe. The symbol must be shown in outline in all applications.
Own work using: iso.org/obp/graphics/grs/e6ff6f94-2fc6-4927-aba8-b0b1cfd61b6c 200.png
Vectorization:  Mrmw