Last reviewed and updated: 2026-09-24
If you smell gas right now: leave the building immediately. Do not switch anything electrical on or off, do not use a phone inside, and do not look for the source yourself. From outside and well clear of the property, call 911 and your gas utility. Detection work happens only after the property has been made safe.
Natural gas is odorless, so utilities add mercaptan to give it the distinctive rotten-egg smell. That smell, a hissing sound near a line or appliance, dead vegetation in a line along the yard, or unexplained dizziness and headaches indoors are all reasons to evacuate and call for help. Once the property is safe, gas line testing uses pressure testing and electronic gas detectors to find the failure point before any repair is made.
Gas is a safety call first and a detection job second. Water-side work such as slab leaks and service line leaks is handled separately, and priced separately on the cost guide.
Warning signs
- A rotten-egg or sulphur smell: the added odorant
- Hissing or whistling near a gas line, meter or appliance
- A patch of dead or dying vegetation in a line across the yard, above a buried gas line
- Bubbling in standing water over a buried line after rain
- Dizziness, headaches, nausea or fatigue that improve when you leave the house
- An unexplained rise in gas usage with no change in habits
- Soot or yellow appliance flames where the flame should be blue
What to do, in order
- Get everyone out. People and pets, immediately, without stopping to investigate.
- Touch nothing electrical. No light switches, no garage door, no appliances, no phones inside. A spark is the danger.
- Leave doors open behind you if you can do so without delay.
- Call 911 and your gas utility from outside, well clear of the property.
- Do not go back in until emergency services or the utility say it is safe.
- Arrange line testing afterwards to locate the failure and confirm the system holds pressure.
How gas lines are tested once it is safe
Gas leak location is a different discipline from water leak detection. The line is isolated and put under pressure with a gauge; a line that will not hold pressure has a leak. Electronic combustible-gas detectors and a soap solution at joints and fittings then narrow it to the failure point. Buried lines are traced and surveyed along their route.
Common failure points are corroded buried steel line, flexible connectors at appliances, threaded joints where sealant has aged, and damage from digging or landscaping work.
Frequently asked questions
What should I do if I smell gas in my house?
Leave immediately with everyone in the building. Do not switch anything electrical on or off, do not use a phone inside, and do not try to find the source. From outside and well clear of the property, call 911 and your gas utility. Do not return until you are told it is safe.
What does a gas leak smell like?
Rotten eggs or sulphur. Natural gas is naturally odorless, so utilities add a chemical called mercaptan specifically so leaks can be smelled. If you notice that smell, treat it as real.
Can you have a gas leak without smelling anything?
Yes. A buried line leaking outdoors can vent into the soil, and the odorant can be partially filtered by the ground. Signs to watch for are a strip of dead vegetation above a buried line, bubbling in standing water after rain, hissing near the meter, or an unexplained rise in gas usage.
How is a gas leak located once the property is safe?
The line is isolated and pressure tested, a line that will not hold pressure has a leak. Electronic combustible-gas detectors and soap solution at joints and fittings then narrow it to the failure point. Buried lines are traced and surveyed along their route.
Where do gas leaks usually occur?
Corroded buried steel line, flexible connectors at appliances, threaded joints where the sealant has aged, and lines damaged by digging or landscaping. Appliance connections are the most common indoor source.
Are carbon monoxide and a gas leak the same thing?
No. A gas leak is unburned natural gas escaping and is an explosion risk. Carbon monoxide is a by-product of incomplete combustion from an appliance, is odorless and colorless, and is a poisoning risk. Both are emergencies, and every home with gas appliances should have working carbon monoxide alarms.