Undetected: A deadly 1937 school explosion led to odorization requirements for combustible gas

Looking Back...  Undetected: A deadly 1937 school explosion led to odorization requirements for combustible gas, NFPA Journal®, September/October 2010

With few exceptions, the U.S. Code of Federal Regulations requires 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."

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