Hydrogen safety

The Hindenburg disaster is an example of a large hydrogen explosion.

Hydrogen safety covers the safe production, handling and use of hydrogen, particularly hydrogen gas fuel and liquid hydrogen. Hydrogen possesses the NFPA 704's highest rating of four on the flammability scale because it is flammable when mixed even in small amounts with ordinary air. Ignition can occur at a volumetric ratio of hydrogen to air as low as 4% due to the oxygen in the air and the simplicity and chemical properties of the reaction. However, hydrogen has no rating for innate hazard for reactivity or toxicity. The storage and use of hydrogen poses unique challenges due to its ease of leaking as a gaseous fuel, low-energy ignition, wide range of combustible fuel-air mixtures, buoyancy, and its ability to embrittle metals that must be accounted for to ensure safe operation.[1]

Liquid hydrogen poses additional challenges due to its increased density and the extremely low temperatures needed to keep it in liquid form. Moreover, its demand and use in industry—as rocket fuel, alternative energy storage source, coolant for electric generators in power stations, a feedstock in industrial and chemical processes including production of ammonia and methanol, etc.—has continued to increase, which has led to the increased importance of considerations of safety protocols in producing, storing, transferring, and using hydrogen.[1]

Hydrogen has one of the widest explosive/ignition mix range with air of all the gases with few exceptions such as acetylene, silane, and ethylene oxide, and in terms of minimum necessary ignition energy and mixture ratios has extremely low requirements for an explosion to occur. This means that whatever the mix proportion between air and hydrogen, when ignited in an enclosed space a hydrogen leak will most likely lead to an explosion, not a mere flame.[2]

There are many codes and standards regarding hydrogen safety in storage, transport, and use. These range from federal regulations,[3] ANSI/AIAA,[4] NFPA,[5] and ISO[6] standards. The Canadian Hydrogen Safety Program concluded that hydrogen fueling is as safe as, or safer than, compressed natural gas (CNG) fueling,[7]

  1. ^ a b "Hydrogen Safety" (PDF). Office of Energy Efficiency and Renewable Energy.
  2. ^ Utgikar, Vivek P; Thiesen, Todd (2005). "Safety of compressed hydrogen fuel tanks: Leakage from stationary vehicles". Technology in Society. 27 (3): 315–320. doi:10.1016/j.techsoc.2005.04.005.
  3. ^ Cadwallader, L. C.; Herring, J. S. (1999). Safety Issues with Hydrogen as a Vehicle Fuel (Technical report). doi:10.2172/761801.
  4. ^ "AIAA G-095-2004, Guide to Safety of Hydrogen and Hydrogen Systems" (PDF). AIAA. Retrieved 2008-07-28.
  5. ^ "List of NFPA Codes & Standards". NFPA.
  6. ^ "ISO/TC 197 – Hydrogen technologies". www.iso.org.
  7. ^ "Canadian Hydrogen Safety Program testing H2/CNG". Hydrogenandfuelcellsafety.info. Archived from the original on 2011-07-21. Retrieved 2010-07-05.