First Signs of a Gas Leak: What Should I Do?
If you smell gas, hear hissing near a gas line, or see a sign of escaping gas, leave the building or area immediately. Don't stop to find the source. Don't touch lights or appliances, start a vehicle, light a flame, or use your phone inside. Once you're a safe distance away, call 911. Report what you noticed. The gas utility and emergency responders decide when the property's safe to re-enter.
Possible gas-leak signs and the safe response
| Sign | Why it matters | Safe response |
|---|---|---|
| Rotten-egg or sulfur odor | Utilities add an odorant to help people notice a possible leak | Leave immediately. Call 911 and the gas utility from a safe location |
| Hissing, blowing, or roaring sound | Gas may be escaping near an appliance, meter, pipe, or outdoor line | Do not investigate or operate a valve. Move away and report it |
| Dead vegetation, blowing dirt, bubbles, or vapor outdoors | A pipeline or service-line release can disturb the area around it | Keep away from the area and call from a safe location |
| CO alarm or headache, dizziness, nausea, or confusion | Carbon monoxide is a separate, odorless combustion hazard | Get everyone to fresh air and call 911. Do not stay to find the source |
| Odd furnace behavior after clearance | A combustion, venting, or equipment problem may still need diagnosis | Keep the equipment off until responders clear it, then arrange HVAC service |
What are the first signs of a gas leak?
The most familiar warning is a sulfur or rotten-egg smell. Natural gas doesn't naturally have that smell. Utilities add an odorant like mercaptan so people can notice a possible leak. Take an odor near a furnace, water heater, gas range, meter, outdoor service line, or another gas appliance seriously, even if you can't tell exactly where it's coming from.
Sound can provide another clue. A small leak may produce a faint hiss, while a larger release may sound like blowing or roaring. Outside, watch for dead or discolored vegetation, dirt blowing from the ground, bubbling water, vapor, or an unusual smell near a pipeline or service line. These signs don't prove a leak, but they're enough reason to keep away and call from a safe location.
- You do not need to confirm the smell or sound before leaving.
- Do not search closets, crawl spaces, basements, or the furnace room for the source.
- Do not go back to check whether a faint or disappearing odor returns.
What should I do if I smell gas inside?
Leave the building immediately and take everyone with you, including pets, if you can do it without delaying your exit. Walk away from the building or suspected leak area. Don't use a vehicle to leave from inside a garage or drive through a vapor cloud.
As you leave, don't touch lights, thermostats, appliances, breakers, or other electrical equipment. Don't smoke, light a match, use a lighter, operate a garage-door opener, or use your phone inside. From a safe location, call 911, then contact the gas utility using the emergency number on your bill or its official website.
- Tell other people to stay away if you can do so without approaching the suspected leak.
- Do not pull plugs, reset breakers, move an appliance, tighten a connection, or remove a furnace panel.
- Do not operate the gas meter or a pipeline valve unless emergency officials or the utility direct you to do so safely.
- Do not return until emergency officials or the utility say it is safe.
How is carbon monoxide different from a gas leak?
Carbon monoxide, or CO, is a separate hazard. It has no smell and no color, so the absence of a rotten-egg odor doesn't rule it out. Fuel-burning furnaces, water heaters, fireplaces, stoves, and other equipment can produce CO when combustion, venting, or operation isn't right.
If a CO alarm sounds, or anyone has a headache, dizziness, weakness, nausea, vomiting, chest pain, shortness of breath, confusion, or unusual fatigue, get everyone to fresh air and call 911. Don't stay inside to find the appliance or restart the furnace after leaving. Emergency officials decide when the home's safe.
- A gas smell points to possible escaping fuel; a CO alarm points to an odorless combustion hazard.
- Either warning calls for prompt action and fresh air.
- Do not try to diagnose the source before getting people out.
When should we inspect the furnace?
Call us once emergency responders or the gas utility have evaluated the situation and cleared the property. That's the right time to address a furnace that won't start, repeated shutdowns, unusual combustion behavior, damaged venting, or a heating problem that began before the odor or alarm.
Write down what happened while the details are fresh: the equipment involved, what you smelled or heard, whether a CO alarm sounded, what responders found, and whether the system was shut off. Don't restart the equipment just to reproduce the symptom. Once the property's safe, we can diagnose the equipment, explain the repair, and test it against the original problem.
- Follow the gas utility or emergency responders' instructions for re-entry and equipment shutoff.
- Keep the furnace and other gas appliances off until authorities clear them.
- Schedule annual service for fuel-burning equipment and keep CO alarms installed and tested as directed.
Questions that come up next
What does a gas leak smell like?
Utilities add a sulfur or rotten-egg odorant to natural gas so people can notice a possible leak. Hissing, blowing dirt, bubbles, vapor, dead vegetation, or an unusual smell near a line also deserve caution.
Should I turn off the furnace if I smell gas?
Leave the building first. Don't touch switches, thermostats, equipment, or a gas valve if doing so keeps you in the suspected area. Ask emergency responders or the gas utility what to do from a safe location.
What if the gas smell goes away?
Don't treat a fading odor as proof the home's safe. Leave and report what you noticed. Only emergency officials or the gas utility can determine whether the property's safe to re-enter.
Can an HVAC technician check a gas smell?
Only after responders or the gas utility handle the immediate hazard and clear the property. An active suspected gas leak is an emergency-safety matter, not a routine HVAC visit.
Need HVAC help in Frederick?
Tell us what the system is doing and what you've checked already. If it needs a visit, we'll say so.