NFPA Journal - November/December 2020 - 56

GAS LEAKS ON THE RISE
Deadly gas explosions aren't a new problem. A massive
natural gas explosion in 1937 destroyed a school in New
London, Texas, killing nearly 300 children and teachers. The
Quarterly, the NFPA magazine at the time, observed that
"there is evidence of a most terrific force in the great extent
of devastation and loss of life that came almost instantly;
testimony of bodies tossed 75 feet into the air; an automobile
200 feet distant crushed like an eggshell under a two-ton
slab of concrete." According to NFPA data, the event is the
15th-deadliest fire or explosion in US history.
While no data exists to support an increase in gas explosions or fires over time, the data does show a sharp increase
in leaks in the past 10 to 20 years. From 2007 to 2016, the
annual number of US fire department responses to residential gas leaks jumped by over 40,000, from about 100,000 to
141,000, according to the 2018 NFPA report.
A leading theory for this increase is the fact that America's
gas pipeline infrastructure is aging. In the days following
the Merrimack Valley explosions, for example, USA Today
reported that one out of every four miles of gas mains in
Massachusetts had been installed prior to 1940. When a gas
explosion shredded a block of buildings in the East Harlem
section of New York City in 2014, killing eight and injuring
nearly 50 more, it was discovered that the leaking pipe had
been installed in the 1800s. Last year, the Conservation
Law Foundation, an environmental advocacy group based
in New England, called the country's aging gas infrastructure "expensive, leaky, and dangerous." And less than a year
before the deadly Baltimore explosion, the Baltimore Sun ran
an article ominously warning readers that the city's "natural
gas system is increasingly leaky."
The cause of gas leaks can usually be traced to one of three
factors: the gas utility's equipment, equipment on private
property, or gas appliances. In the Merrimack Valley incident, the leaks were traced to the gas distribution system of
the utility, Columbia Gas. According to the National Transportation Safety Board, highly pressurized natural gas was
accidentally released into a distribution system designed for
low-pressure gas. The over-pressurized gas raced into homes
and other structures, overwhelming household systems and
flooding spaces with natural gas vapors.
When an event like this occurs, it doesn't take much gas
to create conditions capable of producing fires or explosions.
The concentration of propane vapors in the air needed to
spark a fire-known as the lower flammability limit (LFL)-is
only about 2 percent. For natural gas, it's closer to 5 percent.
When the LFL is reached, an ignition source can come from
something as seemingly innocuous as flipping the switch
to turn on an appliance. That's why emergency officials in
the Merrimack Valley region quickly ordered the shutoff of

4,200 125,000
Average number
of natural gas fires
in homes in the
US each year

Average number of
residential gas leaks fire
departments respond to
in the US each year

electricity once explosions and fires began to occur. Despite
those efforts, more than 130 buildings in three communities
were damaged by fires or explosions, including five that were
completely destroyed.
DETECTION IS KEY
Replacing aging gas pipeline infrastructure is costly and
time-consuming, which is why bolstering gas detection measures is the next most logical step to improve safety.
For the vast majority of the general public, the only gas
detectors they have are their noses. Gases like natural gas and
propane are laced with mercaptan, a harmless, distinct-smelling chemical, so you know when there's a leak. But "odor fades
and not everyone can detect odor readily," Alexander Ing, an
engineer in the Hazardous Materials division at NFPA, wrote in
a blog posted the day after the Baltimore incident. Studies show
that human smell succumbs to a phenomenon known as olfactory fatigue after a minute or two of being exposed to the same
odor, meaning you can no longer smell it.
Plus, if a leak occurs underground, the earth can essentially extract the mercaptan out of the gas. This happened in
the Maine incident, after an underground propane gas line
was punctured by a company performing construction work
on the property. A few days later, a maintenance worker
reported the smell of gas to authorities, but when firefighters
arrived, no smell could be detected in certain parts of the
building. "When they used gas detection meters, though,
they were picking up high readings," said Maine State Fire
Marshal Joe Thomas. "So that mercaptan was actually
scrubbed out of the gas by the earth it was moving through."
About a month after the explosion, Lois Reckitt, a Maine
state representative, proposed a bill to require gas detectors
on certain properties in the state. "There are no regulations,
and I just thought that's crazy, especially with what just happened in Farmington," she told local news reporters at the
time. The bill is still being considered by state lawmakers,
who are in recess due to the COVID-19 pandemic.
Currently, anyone can go out and buy a gas detector-and
there is a UL standard for their performance-but there's
no comprehensive guidance on installing them, said Olenick, the NFPA 715 technical committee chair who works
as an engineer at Maryland-based Combustion Science &
Engineering. "You could perhaps look at the manufacturer
instructions, but there's really no prescriptive requirements,"
he said. "That was where the push for the standard came
from, and it's our hope that the standard will provide guidance to these municipalities and to the Life Safety Code® and
to model building codes. They will have a standard that will
tell them how to properly install these devices."
The road to standardization officially began in August 2018,
when the American Gas Association sent a request to NFPA for

100,000

141,000

2007

2016

Residential gas
leaks in the US in

An increase of

41%

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NFPA Journal - November/December 2020

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