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Safety Alert From the PHMSA: Risks Associated with LPG Odor Fade

Safety Alert From the PHMSA: Risks Associated with LPG Odor Fade

Published in the July 17, 2013 Federal Register, the purpose of this Safety Alert Notice from the PHMSA is to advise Shippers and Carriers of HazMat of the risks associated with the under-odorization of Liquefied Petroleum Gases (LPG).

LPG is an odorless and colorless gas that is also highly flammable and dangerous to inhale in large quantities.  For that reason, LPG is generally required to be odorized or stenched when offered and transported in commerce in order to indicate the presence of the LPG in the event of an unintended release or leak.  The Hazardous Material Regulations (HMR) at 49 CFR 173.315(b)(1) require that all LPG in cargo tanks and portable tanks (defined later in this article) be effectively odorized.  However, odorization is not required if it would be harmful or if odorization will serve no useful purpose as a warning agent during further processing.  In practice, these exceptions from odorization apply to LPG’s transported to an industrial end-user.  LPG odorization is also not required if it is offered or transported in rail tank car tanks or cylinders (defined later in this article) no matter its intended use.  Meanwhile, multiple Federal and State laws require LPG intended for use by non-industrial entities to be odorized or stenched.  In addition, even when odorized, it has been noted by PHMSA that new or recently cleaned tanks may absorb the odorant into the metal shell of the tank, resulting in under odorization.

Despite existing regulations, the PHMSA has determined that under odorization or odor-fade of LPG has prevented its detection in the event of unintended leaks.  Non-detection of leaked LPG has resulted in an unacceptable amount of injuries and fatalities; such as an incident that took place July 30, 2010 in Norfolk, MA where an explosion occurred at a residential condominium complex under construction.  This Safety Alert Notice does not contain any revisions or additions to the HMR, it does however contain several recommendations for both shippers and carriers to enhance the transportation safety of LPG.

PHMSA recommendations contained in this Safety Alert Notice include:
  • All LPG transported in rail tank car tanks and/or cylinders be odorized per §173.315(b)(1) unless it would be harmful in the further use or processing of the LPG or if it will serve no useful purpose.
  • During odorization of LPG by a manual injection process, quality control checks should be conducted to ensure that the requisite amount of odorant is being injected.
  • When odorization of LPG is automatically injected, equipment calibration checks should be periodically performed to ensure consistent injection levels of the required odorant.
  • Persons who receive new or recently cleaned tanks for filling with LPG should be notified of this fact and persons filling new or recently cleaned tanks should implement appropriate quality control measures to ensure that potential odorant fade is adequately addressed.
Helpful definitions from 49 CFR 171.8:

Cargo tank means a bulk packaging that:

(1) Is a tank intended primarily for the carriage of liquids or gases and includes appurtenances, reinforcements, fittings, and closures (for the definition of a tank, see 49 CFR 178.320, 178.337-1, or 178.338-1, as applicable);

(2) Is permanently attached to or forms a part of a motor vehicle, or is not permanently attached to a motor vehicle but which, by reason of its size, construction or attachment to a motor vehicle is loaded or unloaded without being removed from the motor vehicle; and

(3) Is not fabricated under a specification for cylinders, intermediate bulk containers, multi-unit tank car tanks, portable tanks, or tank cars.


Cylinder means a pressure vessel designed for pressures higher than 40 psia and having a circular cross section. It does not include a portable tank, multi-unit tank car tank, cargo tank, or tank car.


Portable tank means a bulk packaging (except a cylinder having a water capacity of 1000 pounds or less) designed primarily to be loaded onto, or on, or temporarily attached to a transport vehicle or ship and equipped with skids, mountings, or accessories to facilitate handling of the tank by mechanical means. It does not include a cargo tank, tank car, multi-unit tank car tank, or trailer carrying 3AX, 3AAX, or 3T cylinders.


Rail car means a car designed to carry freight or non-passenger personnel by rail, and includes a box car, flat car, gondola car, hopper car, tank car, and occupied caboose.

 For further information about this Safety Alert Notice, contact:

Charles Betts, Director at charles.betts@dot.gov or Delmer Billings, Senior Regulatory Advisor at delmer.billings@dot.gov

If you have any questions about the transportation of hazardous materials or the PHMSA training requirements for HazMat Employees, don’t hesitate to contact me.