Information on Natural Gas Odorant and Gas Pipeline Purging

UGI Utilities, Inc. - Safety Bulletin

The purpose of this Safety Bulletin is to provide contractors, who work on natural gas piping, appliances and equipment, and customers with additional safety information on natural gas odorant, the potential for odor fade, and hazards associated with purging gas in natural gas piping.

Odorization

• Natural Gas is odorized to alert customers and others in the vicinity to leaks, which can create a safety hazard.  
• UGI Utilities, Inc., and its associated companies, UGI Penn Natural Gas, Inc., and UGI Central Penn Gas, Inc., comply with applicable state and federal regulations governing the odoriziation of natural gas. 
• These regulations generally require that natural gas odorant be added to natural gas in sufficient quantities to produce a smell that is readily detectable under specified conditions by a person with a normal sense of smell. 

Can You Smell It?

While natural gas is odorized to assist in the detection of leaks, you should not rely solely on your sense of smell to determine if a gas leak exists or if natural gas is present at unsafe levels.  Some individuals may experience a reduced sensitivity to the odorant because:

• They have a cold, allergies, sinus congestion or another medical condition that has an effect on their sense of smell. 
• Their sense of smell is reduced due to the use of tobacco, alcohol or drugs. 
• Tobacco smoke, cooking odors and other strong odors can mask the smell of natural gas.
• They have a diminished sense of smell for other reasons. 

Odor Fade

• Odor fade (diminished level of odorant concentration) occurs when the level of odorant in gas is reduced due to physical and/or chemical processes.  
• In gas piping systems, odor fade occurs predominantly in installations of new pipe, rather than in existing pipe. 
• Odor fade is more pronounced in new steel pipe of larger diameters and longer lengths.  However, odor fade can also occur in plastic pipe, and in smaller and/or shorter pipe installations.  
• New pipeline installations or additions of new piping segments, may require the purging of the pipe before it is placed into service to prevent occurrences of odor fade. 
• Other factors that may cause odor fade include: the construction and configuration of the facility; the presence of rust, moisture, liquids or other substances in the pipe; and gas composition, pressure and/or flow. 
• Intermittent, little or no gas flow over an extended period of time may also result in the loss of odorant until gas flow increases or becomes more frequent.  If natural gas is leaking underground, its passage through soil may reduce the smell.  
• This list of factors that may cause odor fade is not intended to be exhaustive. 

Purging Gas:

• Never purge the contents of a gas line into a confined space.  
• Purging a gas line should be performed by a qualified professional and should be done in a well-ventilated area or by venting the contents to the outside atmosphere.  
• Always use gas detection equipment during purging operations and when working on gas piping systems, to ensure that no natural gas is present that may result in a combustible or hazardous atmosphere.  
• The personnel conducting the purging process must be and remain in attendance at all times and may not leave the immediate area.  
• Do not rely on your sense of smell to detect the presence of natural gas.  
• Consult your local plumbing code, mechanical code, fuel gas code and/or your department of building and safety for more information.  
• When installing gas appliances or equipment, the manufacturer’s instruction manual should be followed in accordance with the guidance of the local code authority.