Venting of Low Pressure Hydrogen Gas: A Critique of the Literature1

The use of hydrogen is increasing in industrial processes, and its use is likely to increase further with its potential use as an energy carrier. The venting of hydrogen is inevitable at some time for almost all uses, and its propensity to ignite makes it essential that safe venting regimes are understood. The options for disposal by dilution to below the lower flammable limit, inerting, dispersion of flammable concentrations and flaring are discussed, along with the potential for ignition of releases within the flammable range and the subsequent need for flame extinguishing. The available literature on the protection of vents from external ignition is critically examined, to determine the appropriate parameters to allow selection of a disposal method. A decision-tree is presented to allow a rational appraisal of the most appropriate disposal method to be selected and precautions to be applied for adequate protection of the vent.