Gas detection. When dispatched to investigate an
odor of gas, notify the utility company immediately.
Utility company employees are trained and equipped
with gas detecting instruments. Odors can come from
many causes, including petroleum products such as
gasoline, propane, marsh gas, sewer gas and industrial
flammable gas/lower explosive limit (LEL) meters. It
is important to clearly understand what a meter reads
and any limitations of that meter.
For some meters, high gas concentrations that result
in an oxygen-depleted atmosphere may result in an
inaccurate reading of the level of flammable gas and
potentially a false low reading of LEL. Also understand that the LEL is a percent. For example, the LEL
of natural gas is approximately five percent, meaning
that if there is five percent of natural gas in a mix with
95 percent air, there is enough gas to result in a fire/
explosion. In this case, if a LEL meter is being used,
calibration gas, and there may be some variation in
reading in the field to a gas that is different than the
calibration gas) and because of incomplete mixing of
the natural gas in the space being metered (since it is
lighter than air, natural gas may tend to collect in the
upper spaces of a room/area or in other areas where
air movement is incomplete).
Responding crews must attempt to identify the type
of gas causing the odor and the source of the leak.
Gas meters that read LEL need to be used to determine where the hot zone is. Firefighters must realize
A basic knowledge of natural gas and how to eliminate
or control hazards can make an incident run much more
smoothly and ensure the safety of all personnel on scene.