Gas smell: leave now, call the utility from outside
Natural gas is odorized with mercaptan so a leak smells like rotten eggs. The American Gas Association's instruction is to leave the building immediately and call 911 or the gas utility from a phone away from the area.
What is probably happening
- A gas leak at the furnace, water heater, stove, or the piping between them.
- A furnace that failed to light and let unburned gas into the cabinet can also cause a brief whiff. A smell that lingers or grows is a leak.
- Utilities add the rotten-egg odorant precisely so you notice. Trust your nose.
Do this in the next five minutes
- Walk out. Leave the door open behind you.
- Do not touch light switches, the thermostat, the garage door opener, or your phone until you are outside. A spark can ignite gas.
- From outside, call 911 or the gas company's emergency line. The number is on your bill and on the meter.
- If you can safely reach the meter outside, the utility may talk you through shutting it off. Otherwise leave it to them.
- Follow the instructions of the utility crew or firefighters who arrive. They decide when it is safe to go back in.
Do not
- Do not try to find the leak yourself, and do not light anything.
- Do not start a car in an attached garage.
- Do not call an HVAC company first. The utility responds to leaks and makes the house safe. The HVAC technician comes after, to repair the appliance.
Who to call
Gas utility first, then a licensed HVAC technician
The utility finds the leak and shuts off the gas. A licensed HVAC contractor repairs a leaking furnace valve or connection once the utility has cleared the house.
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What it should cost
$64 to $1,475
Furnace repair, national range, averaging $318. The utility's emergency response is separate
Source: Angi, furnace repair cost, updated August 2026. View source
National published range, not a quote for your job. The full cost table for this trade is on the hvac page.
Ask this contractor, on the phone, before anyone comes out
Tap each one as you ask it.
- Did the utility tag a specific appliance or fitting as the leak? Can you repair exactly that?
- Will you pressure-test the gas line and show me the result?
- Are you licensed in this state for gas appliance work, and what is the license number?
- Is a permit required for this repair here, and will you pull it?
End the call if
- A contractor who wants to relight and run the furnace before the utility has cleared the house.
- A whole-system replacement pushed on the spot with no leak test shown to you.