Molecular seals and Velocity or fluidic seals are used to limit the required "sweep flow" or "purge flow". A "sweep flow" is required to prevent air impingement in the process header when there is little or no process flow going to the flare. Should air enter the Flare or vent header, a release of process gas could result in a combustible mixture present within a restricted area. The ignition of this gas - air mixture can result in an explosion, and cause severe equipment damage.