API Std 537 pdf download.Flare Details for General Refinery and Petrochemical Service 3 Definition ofTerms Terms used in this Standard as they relate to flares are defined in 3.1 through 3.68. 3.1 air seal: A device used to minimize or eliminate the intrusion of air back into the riser from the exit. 3.2 assist gas: Fucl gas that is added...