“Explosion Vents are low pressure relieving devices with large area which provides an effective and economic method of preventing explosions from reaching their potential maximum pressures. During normal venting, an explosion is freely discharged, allowing flames and dust to exit the process vessel being protected.”
Reference: Chemical Process Industry Safety, 1st edition By K S N Raju, and Loss Prevention in the Process Industries, Frank P. Lees.
Comment: the definition is given for venting a dust explosion, but holds as well for a gas explosion. Batch or semi-batch reactors are often also protected against explosion by a vent. Vent design is a specialized field of knowledge. The latter reactor vents are difficult to size due to two-phase flow and reacting fluid leaving the reactor. AIChE’sDIERS, the Design Institute of Emergency Relief Systems, provides design calculation methods.