Hydrogen has a long history of safe use in the chemical and aerospace industries. An understanding of hydrogen properties, proper safety precautions and engineering controls, and established rules, regulations, and standards are the keys to this successful track record.
As the use of hydrogen and fuel cell systems expands, codes and standards will be needed to provide the information to safely build, maintain, and operate hydrogen and fuel cell systems and facilities, to ensure uniformity of safety requirements, and to assure local code officials and safety inspectors that sufficient safety standards have been met.
What Are Codes and Standards?
Codes and standards are needed to enable the safety of hydrogen and fuel cell systems and to facilitate the use of hydrogen as a fuel. Building codes and equipment standards provide a systematic and accurate means of measuring and communicating product risk and insurability to the customer, general public, and fire-safety certification officials.
"Codes" are established by jurisdictions—for example, building codes, fire codes, building ordinances, etc. Today, there are over 44,000 jurisdictions in the United States, and some of these existing jurisdictional codes could affect hydrogen use. "Standards" are agreed upon to enable consistency, compatibility, and safety. Many organizations are cooperating in the development of codes and standards to enable safety and encourage the safe commercialization of hydrogen uses.
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Comparison of Hydrogen to Conventional Fuels
With proper handling and controls, hydrogen can be as safe as, or safer than, other fuels we use today. Safety considerations associated with handling hydrogen include fire, explosion, and asphyxiation. Below is a chart that shows how hydrogen compares with some common fuels.
Properties of Hydrogen, Natural Gas, Gasoline, and Propane
|Hydrogen (gas||Natural Gas (gas)||Gasoline (liquid)||Propane (liquid)|
|Lower heating value (Btu/lb)||51,532||21,300||18,000–19,000||19,800|
|Density at standard conditions (lb/gal)||0.0007a||0.005a||6.0–6.5a||4.22|
|Autoignition temperature in air (°F)||1,050–1,080||1,004||495||850–950|
|Volume concentrations for flammability in air (%)||4.1–74||5.3–15||1.4–7.6||2.2–9.5|
|Diffusion coefficient in air (in.2/sec)||0.0946b||0.0248b||0.008b||0.017c|
|Toxicity to humans||Non-toxic, simple asphyxiant||Non-toxic, simple asphyxiant||Poisonous, irritant to lungs, stomach, and skin||Non-toxic, simple asphyxiant|
Sources: All values are from DOE Alternative Fuels Data Center, except as follows:
a Clean Air Program: Design Guidelines for Bus Transit Systems Using Hydrogen as an Alternative Fuel. U.S. Department of Transportation. DOT-VNTSC-FTA-98-6, 1998. Table 2.1.
b Hydrogen Energy System: A Permanent Solution to Global Problems. T. Nejat Veziroglu. University of Miami. Coral Gables, FL.
c Guidelines on Remediation of Contaminated Sites. Appendix 5.5, "Physical and Chemical Data."