Natural gas is colorless and odorless. Utilities add mercaptan (the rotten-egg smell) so leaks become detectable at concentrations far below the explosive threshold. Smell is the most reliable first sign, but eight other indicators can signal a leak. Knowing the 9 signs and the exact emergency protocol can prevent property damage and save lives. This is the household safety guide every US gas-customer family should read.
The 9 signs to recognize
One: rotten-egg or sulfur smell indoors. Most reliable single sign. Two: hissing or whistling near an appliance or gas line. Three: sudden unexplained bill spike of 30 percent or more. Four: dizziness, nausea, or headaches that resolve when leaving the home.
Five: dead or yellowed vegetation along outdoor gas line routes. Six: dirt blowing from a hole or crack in the ground near the meter. Seven: bubbling in standing water near the meter or gas line. Eight: visible damage to the gas meter or attached piping. Nine: pilot lights repeatedly extinguishing on gas appliances.
The 7-step emergency protocol
If you smell gas indoors: leave the home immediately. Do not switch lights or any electrical devices on or off. Do not use cell phones inside. Do not light matches or smoke. Call the utility emergency line from outside. Stay outside until the utility tech confirms it is safe.
Every US gas utility runs a 24-hour emergency line. They dispatch a technician for free, regardless of who supplies your gas. Keep the utility emergency number saved in your phone.
Prevention basics
Install carbon monoxide and gas detectors near each gas appliance. Schedule annual furnace inspections through your gas utility (most offer free or subsidized inspections).
Never run unvented gas appliances (space heaters, gas dryers without proper venting) in enclosed rooms. Always provide combustion air per appliance manufacturer specs. Replace gas appliances showing yellow or orange flames (should burn blue) immediately.
Lock the rate before the next reset.
Seenra runs the supplier shortlist in 5 minutes. No credit pull, no on-site visit, no service interruption. Forever free for households.
Get my fixed-rate quote →Common questions
Quick answers from the editorial desk
Who do I call if I smell gas?
Should I open windows during a suspected gas leak?
Should I shut off the main gas valve myself?
Why is mercaptan added to natural gas?
Further reading