Detecting a Gas Line Leak — Part Two of a Series


(Part Two of a series aimed at neighborhood or workplace teams)

“Do you smell gas?”

“Could this be leaking? What is it carrying, anyway?”

If you are concerned about the potential for a gas line leak, you probably want to start by finding the location of gas lines in your neighborhood. You will discover that this takes some time and effort!

Still, using the online resources and your local utility, as described in Part One of this series, you can usually get a good start.

You will note that there are three main types of gas lines:

  1. Transmission lines — Long-distance lines, typically more than 10” in diameter (can be as big as 42”), move large amounts of gas under high pressure (200 – 1,200 psi).
  2. Distribution or main lines –- These lines operate at intermediate pressure (up to 200 psi) and are 2″ to 24″ in diameter.
  3. Feeder or service lines – These are the lines that actually connect to your home. They are not so easy to track once they disappear underground. Typically they are less than 2” in diameter, and they carry odorized gas at low pressures, below 6 psi.

For a local emergency response group, your feeder or service lines are probably what you’ll be looking for. But we have to repeat, utility companies are concerned about vandalism and sabotage or even terrorism, so they don’t publicize the location of these lines. Think persistence and relationships!  We were actually able to get the construction drawings showing location and sizes of the gas lines for our community.

Action item: create a map of your neighborhood, showing the different gas lines as you identify them. If possible, note the location of shut-off valves.

Should we assume we’ll experience a local gas line leak?


The gas distribution system is made up of thousands of miles of pipelines, and they operate safely most of the time. Still, all of the time, the system is under one or another source of stress.

Stresses include:

  • Built-in weaknesses from poor connections, bad welds or incorrectly installed equipment
  • Corrosion or wear from aging
  • Weather-related shifts (winter freeze-thaw cycles) Think of the extreme weather events we’ve experienced in the past couple of years!
  • Seismic shifts or earthquakes

And, of course, there are construction accidents where a hand shovel or large piece of equipment punctures a line.

Just to give you an idea, I cut this out of the news yesterday.  There are notices like this every day!

Gas line leaks reported

. . . from the news yesterday

It is the responsibility of the system operators to monitor and maintain the pipelines under their jurisdiction.

In some states legislation has been introduced to require the utilities and/or operators to report on leaks and on their progress in fixing them. As you can expect, the utilities oppose this legislation, saying that the number of leaks is exaggerated and that fixing more leaks faster would be too expensive. Find out about legislation in your own state!

Can we prevent a gas line leak in any of these pipelines?


But you can do your community a service by finding out what sort of gas line maintenance takes place.

And, you may be able to prevent a disaster by detecting and reporting a leak!

How can we tell if there’s a leak?

1-Use your nose in and around the house!

The most common indication of a leak is SMELL. An odorizer called Mercaptan is added to feeder lines for the very purpose of making a leak noticeable.

What does Mercaptan smell like? Most people compare it to “rotten eggs.” In any case, it is distinctive and obvious.

If you just aren’t sure what natural gas smells like, spend a few dollars for some “scratch n’ sniff” samples! Makes a great addition to a meeting about gas leaks! Here’s a link to Amazon – 30 stickers like the one shown as the left, only $3.00 when I checked today!

Natural Gas Mercaptan Stickers

2- A gas sniffer will help pinpoint the leak.

If your environment may have more than one suspicious smell, or if you sense you might easily get used to a smell and stop noticing it, consider investing in a gas sniffer. This is a simple hand-held gadget that can identify a leak for sure. Some sniffers tell you what gas is leaking. They use a meter and/or an audio sound (“tic, tic”). As always, the more you pay for equipment, the more functions you get.

Our local emergency response groups own a couple of different ones. The “pen” model (less than $40) is used by one group to check around their emergency gas generator when they start it up.

The “tube” model (around $150) adjusts from broad to fine sensitivity in order to pinpoint the precise location and type of gas that is leaking. We have used this model with startling success, using it to identify a propane leak from a gas BBQ, among other leaks. (We also have a neighbor who insisted she smelled leaking gas. It turns out it was smoke from marijuana coming from a nearby shed. We didn’t pursue to see if its use was legal or illegal!)


Pen style

General Tools PNG2000A Natural Gas Detector Pen


Tube model

UEi Test Instruments CD100A Combustible Gas Leak Detector

Action item: If you suspect or are plagued with frequent leaks, you may want to add a gas sniffer or two to your collection of safety equipment. They are easy to operate and can add a degree of confidence to your suspicions. In a big emergency, a gas sniffer might make it easier to decide to shut off the gas entirely.

Be on the lookout for signs of leaks from larger pipelines.

You’re not likely to find yourself walking along the route of a larger underground pipeline, but a leak can show up anywhere. (We experienced a gas-line break right in front of our community. A back-hoe hit a line that according to the construction crew “wasn’t on the map.” )

Here are some ground-level signs you might notice:

  • An unexpected hissing, roaring sound
  • Dirt or dust blowing up from the ground
  • Water bubbling or spraying
  • A spot of dead or brown vegetation when it’s green everywhere else
  • Flames coming from the ground

As a reminder, the gas in these larger pipes may have no odorants added.

What should we do when we discover a leak?

When you do identify a leak, you need to act quickly and decisively. Your goal is to avoid a build-up of gas around a leak or a build-up from gas “migrating” to a nearby area (such as a basement) – creating conditions for an explosion.

Your first response should be to get safely away from the area (hundreds of feet away!) and then CALL 911 or the gas line operator to GET THE GAS SHUT OFF.

As you move away, warn other people about the danger, too, and encourage them to move to safety.

Above all, DO NOT CREATE A SPARK by flipping a light switch, lighting a cigarette, starting an engine, turning on a battery-operated light, etc.

Action item: Discuss with your group where a break might logically occur in your neighborhood. Identify some ordinary actions that someone might take that could start a gas fire. In our community, starting up the car to “get away from the danger” is likely to be the most dangerous action possible. The catalytic converters of cars in a traffic jam can reach 1,600 degrees – plenty hot enough to start a fire if there is the right mixture of gas!

Is that all we can do? Shouldn’t we turn off the gas?

Calling 911 from a safe distance is the first and most important step. Not creating a spark is the second.

Every member of your family and of your workforce should know and be able to follow this rule.

However, as an emergency response group, there is more you should know and consider when it comes to getting the gas shut off.

We will address some of these options in Part Three of this series.

Your Emergency Plan Guide Team

Got any stories about gas line leaks or explosions? Feel free to share . . .! And don’t miss the first article in this series.



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