Natural gas has no smell. The rotten egg odor is mercaptan, an additive that exists for exactly one reason: so your nose can find a leak before anything else does. If you are smelling it, take it seriously. Here is the drill, from a crew that tests gas lines for a living.
If the smell is strong or you hear hissing
Leave. Do not flip switches, do not unplug anything, do not start the car in the attached garage. Sparks are the enemy. Get everyone outside, leave the door open behind you, and call your gas utility’s emergency line from the street. The utility handles the meter and the supply. That part is free and they are fast.
If it is faint and comes and goes
A faint whiff near the stove when a burner half-lights, or an occasional smell near the water heater, usually means a small leak at a fitting or valve. Shut the appliance’s gas valve if you know where it is, ventilate, and get it tested. Small leaks do not heal. They grow.
What the utility will not fix
Here is the part that surprises people: the gas company owns the line up to your meter. Everything after the meter, the house piping, the flex connectors, the appliance valves, is yours. When the utility tags a leak on the house side, they shut you off and leave, and a licensed plumber takes it from there. That is us. We do gas line repair, new runs for ranges, dryers, fire pits, and generators, and pressure testing to prove the whole system tight before the meter goes back on.
How we test
We isolate the system, put it under pressure with a gauge, and watch. A tight system holds. A leaking system tells on itself, and then we track the drop to the fitting that caused it. Gas is the one trade where close enough does not exist, and we treat every connection that way.
One more thing worth doing
If your house is older, ask us to look at the flex connectors behind the stove and dryer the next time we are out for anything. They age, they kink, and they are cheap to replace on a scheduled visit. Questions, or a smell you are not sure about? (877) 233-1033, 24 hours, Monday through Saturday.