Gas leak: warning signs and what to do immediately (and what never to do)

Natural gas and propane have no smell of their own. Utilities add a strong-smelling chemical, like rotten eggs or sulfur, so you can detect a leak. When you smell it, you have a few minutes in which your decisions matter. Gas explosions in homes and apartment buildings often start with something ordinary: flipping a light switch or ringing a doorbell.

Signs of a leak

• The distinctive smell, like rotten eggs or sulfur, especially near the stove, furnace, meter or in the stairwell.
• A hissing sound near a pipe, valve or appliance.
• A yellow or orange flame on the stove instead of blue (incomplete burning: also a carbon monoxide risk).
• Outside: bubbles in puddles, a strip of dead vegetation, dust blowing above the ground.
• Your gas detector goes off.

What to do immediately

1. Don’t switch anything on or off: lights, appliances, doorbell, elevator. Any spark can ignite gas.
2. Don’t light a flame: lighter, match, cigarette, candle.
3. Open windows and doors wide.
4. Shut off the gas valve if it’s within easy reach without going through the area with a strong smell.
5. Get out with everyone and your pets. Don’t stop for belongings.
6. Warn neighbors by knocking, not by ringing doorbells.
7. Call from outside: your gas utility’s emergency line or the emergency number.
8. Don’t go back in until professionals say it’s safe.

What never to do

• Never look for a leak with a flame.
• Never use a cell phone in the room with the gas.
• Never plug in or unplug anything.
• Never start a car parked in a garage that smells of gas.
• Never repair gas lines yourself.

Propane tanks and cylinders

• Keep cylinders upright, in a ventilated place, away from heat.
• Never store them in a basement or unventilated room: propane is heavier than air and pools low.
• Check the hose and regulator; replace the hose by its expiry date.
• Test for leaks with soapy water, never a flame: bubbles show the leak.

Prevention

• A gas detector in rooms with gas appliances. See our guide to detectors.
• Annual servicing of furnace, boiler and water heater by a licensed professional.
• Never modify gas lines without a licensed fitter.
• Know where the main shutoff valve is and how to close it. Add it to your family emergency plan.

After an earthquake, check for the smell of gas before lighting anything. If in doubt, shut off the main valve. Details in our earthquake guide.