Progress: Not Addressed
DOT Relevance: 192.625
Odorization of gas is considered under Subpart L (Operations) of 49 CFR 192. The Code states that a combustible gas in a distribution line must contain a natural odorant or be odorized so that at a concentration in air of one-fifth of the lower explosive limit, the gas is readily detectable by a person with a normal sense of smell.
Odorants compatible with hydrogen have not yet been found. The sulfur found in traditional natural gas odorants can, even at very low concentrations, damage fuel cells. It is also impractical to implement odorant removal equipment at each point of use.
A successful, efficient, and cost effective method of hydrogen odorization has not yet been identified. Although there are odorants compatible with hydrogen, it is difficult to envision odorizing of hydrogen with sulfur-containing compounds. The Japanese Auto Research Institute (JARI) is working on a non-sulfur based odorant for hydrogen. Other organizations are also actively conducting research on different classes of odorants to make hydrogen leaks detectable by humans. ASME B31.12 will not address this topic.
Current research for hydrogen odorants must address the odorants potential impact on transportation technologies and on end use technologies. Once research is completed, standards for hydrogen odorants must be established and incorporated by reference into the federal code. It may be necessary to re-examine odorant detection limits that are incorporated into 49 CFR 192.