[Federal Register Volume 78, Number 137 (Wednesday, July 17, 2013)]
[Pages 42818-42819]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2013-17120]



Pipeline and Hazardous Materials Safety Administration

[Docket No. PHMSA-2013-0157, [Notice No. 13-10]]

SafetyAlert: Safety Alert: Risks Associated With Liquid Petroleum 
(LP) Gas Odor Fade

AGENCY: Pipeline and Hazardous Materials Safety Administration (PHMSA), 

ACTION: Safety Alert Notice.


SUMMARY: 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 

FOR FURTHER INFORMATION CONTACT: Charles Betts, Director, (email: 
[email protected]) or Delmer Billings, Senior Regulatory Advisor 
(email: [email protected]), Standards and Rulemaking Division, 
Pipeline and Hazardous Materials Safety Administration, U.S. Department 
of Transportation, 1200 New Jersey Avenue SE., Washington DC 20590. 
Telephone: (202) 366-8553, Fax: (202) 366-7435.

SUPPLEMENTARY INFORMATION: PHMSA is aware of several incidents possibly 
attributed to either the under-odorization or odorant fade of liquefied 
petroleum gas (LPG). Most notable of these incidents is one that 
happened in Norfolk, MA on July 30, 2010 where an explosion occurred at 
a residential condominium complex that was under construction. 
Emergency responders from 21 cities/towns deployed personnel to the 
accident site. The accident resulted in seven injuries and one 
    The subsequent investigation raised questions as to whether there 
was a sufficient level of odorant in the LPG contained in the on-site 
storage tanks. In accordance with Federal and State laws and 
regulations, LPG intended for use by non-industrial entities is 
generally required to be odorized, or stenched, to enable the detection 
of any unintended release or leak of the gas. LPG is highly flammable 
and dangerous to inhale in large quantities. The added odorant is a 
safety precaution that helps warn those in the area that a release of 
gas has occurred. In the Norfolk incident, there appeared to be no 
warning, i.e. odorant smell, prior to the explosion, that the on-site 
LPG storage tank was leaking. PHMSA has consulted with stakeholders 
from industry, fire fighter associations, and other regulatory agencies 
in order to better understand the root cause of incidents like the one 
in Norfolk. Although additional research may be necessary in order to 
come to more definitive conclusions, PHMSA has identified situations in 
which the risks of under-odorization or odor fade are more likely to 
occur. These situations are outlined below along with recommendations 
to mitigate potential risk factors that might lead to preventable 
    Injection Process: On December 13, 2012, PHMSA met with 
representatives from the National Propane Gas Association (NPGA) to 
gain a better understanding of the LPG odorization process. During this 
meeting, representatives from the NPGA stated that the most common 
method for the odorization of LPG is through an automated system. 
However, the NPGA also noted there are situations where the odorization 
process is manually performed. Preliminary investigations into the 
Norfolk, MA incident suggest that the lack of sufficient odorization 
rendered the LPG undetectable when the on-site storage tank began to 
leak. In situations where the injection process is not fully automated, 
the potential for human error may increase the possibility of under-
odorization. We believe that the insufficient level of odorant in the 
LPG contained in the on-site storage tank involved in the Norfolk, MA 
incident was likely a major contributing factor in restricting the 
ability of on-site personnel to readily detect the leak. Therefore, in 
this safety alert, PHMSA recommends that when the odorization of LPG is 
being accomplished by a manual injection process, quality control 
checks should be conducted to ensure that the requisite amount of 
odorant is being injected. Additionally, PHMSA recommends that when 
odorization of LPG is automatically injected, equipment calibration 
checks should be periodically performed to ensure consistent injection 
levels of the required odorant.
    New Tanks or Freshly Cleaned Tanks: During our meetings with 
various stakeholders, several indicated that a phenomenon known as 
``odor fade'' may be a problem when new or recently cleaned tanks are 
used. New or recently cleaned tanks may absorb the odorant into the 
metal shell of these tanks, thus limiting the effectiveness of the 
remaining odorant in the LPG. Based on

[[Page 42819]]

this belief, we recommend that persons who receive new or recently 
cleaned tanks be notified of this fact and that persons filling these 
tanks implement appropriate quality control measures to ensure that 
potential odorant fade is adequately addressed. Such quality control 
measures will ensure that when delivered to end users, the LPG has 
sufficient odorant to be detected should a leak occur.
    Odorization Standards: The odorization of LPG is addressed by a 
myriad of Federal and State laws and regulations, as well as, by 
accepted industry standards and practices. When offered and transported 
in commerce, the HMR specifies that all LPG in cargo and portable tanks 
be effectively odorized using either 1.0 pound of ethyl mercaptan, 1.0 
pound of thiopane, or 1.4 pounds of amyl mercaptan per 10,000 gallons 
of LPG, in the event of an unintended release or leak to indicate the 
presence of gas. The HMR do not, however, require LPG to be ordorized 
if odorization would be harmful in the use or further processing of the 
LPG, or if odorization will serve no useful purpose as a warning agent 
in such use or further processing. Essentially, this exception applies 
to LPG being transported to industrial end-users.
    Although the HMR requires odorization of LPG in cargo tanks and 
portable tanks, there are no such requirements in the HMR for rail tank 
car tanks and cylinders. Therefore, in this safety alert, PHMSA 
recommends that all LPG transported in rail tank car tanks or cylinders 
be odorized in accordance with the requirements of Sec.  173.315(b)(1), 
of the HMR, unless odorization would be harmful in the use or further 
processing of the LPG, or if odorization will serve no useful purpose 
as a warning agent in such use or further processing.

    Issued in Washington, DC on July 12, 2013.
Magdy El-Sibaie,
Associate Administrator for Hazardous Materials Safety, Pipeline and 
Hazardous Materials Safety Administration.
[FR Doc. 2013-17120 Filed 7-16-13; 8:45 am]