PHMSA is issuing this safety alert to notify the public of the risks associated with the under-odorization of Liquefied Petroleum Gases (LPG). LPG is an odorless and colorless gas that under certain conditions is required to be odorized for leak detection. The purpose of this alert is to advise shippers and carriers of the recommended procedures to ensure that LPG is properly odorized by all modes of transportation. NOTE: The FRA issued a very similar alert in 2012, CLICK HERE to the alert as it pertains to railcars.