Facts At Your Fingertips: Hydrogen flame hazards and leak detection

The use of molecular hydrogen is common across the chemical process industries (CPI). Annually, 70 million metric tons of H2 are produced worldwide. Most industrial H2 production currently occurs via steam reforming of methane, but production via water electrolysis is growing. This one-page reference provides information on H2 flame hazards and leak detection. Tables 1 and 2 outline major industrial uses of H2 and its key properties, respectively. Hydrogen flammability Although H2 is nontoxic, it is highly flammable and explosive. The National Fire Protection Association (NFPA; Quincy, Mass.; www.nfpa.org) rates H2 as a “4” on the flammability scale (the highest rating), because H2 is flammable when mixed with air, even in small amounts, and the minimum ignition energy (MIE) is small (0.019 mJ for a gas-air mixture). Hydrogen can also self-ignite without energy from an external source when it is leaking from a pipe at high pressure. Hydrocarbon flames differ from H2 flames. AH2 flame emits low levels of infrared radiation and visible light, so it will not give off intense heat and light. Therefore, it cannot be easily detected by human senses. It is difficult to see a H2 flame even up close. Plant workers may see a shimmering,…