Smell Gas Near Your Furnace? Exactly What to Do

Natural gas has no natural odor. Utilities add a chemical called mercaptan that smells like rotten eggs or sulfur, so leaks can be noticed quickly. If you smell that odor near your furnace, water heater, boiler or anywhere in your home, treat it as a potential gas leak. Gas leaks can lead to fires or explosions, and burning gas improperly can also produce carbon monoxide.

This guide explains exactly what to do, what not to do, who to call in Chicago and what happens after the gas company arrives.

The Immediate Steps

1. Get everyone out. Leave the building immediately with all people and pets. Do not stop to gather belongings.
2. Do not create a spark. Do not flip light switches on or off, operate the thermostat, use appliances, unplug anything, ring doorbells, light matches or use a lighter.
3. Do not use your phone inside. Wait until you are outside and away from the building.
4. Leave doors open behind you if it is instant. Do not delay your exit to open windows.
5. Move a safe distance away. Go to a neighbor's home or well away from the building.
6. Call Peoples Gas at 866-556-6002 or 911. Peoples Gas lists 866-556-6002 for gas leaks, and its guidance is to leave the area immediately and call from a safe place.
7. Do not go back inside until the gas company or emergency responders say it is safe.

What Not to Do

• Do not try to find the source of the leak.
• Do not try to repair a gas line or fitting.
• Do not start a car in an attached garage.
• Do not use elevators in multi-unit buildings.
• Do not assume someone else has already called.
• Do not ignore the smell because it seems faint.

Why Leaks Happen Near Furnaces

The area around a furnace, water heater or boiler has many gas connections. Common sources of leaks include:

• Loose or corroded fittings on the gas supply line.
• A failing gas valve inside the appliance.
• Damaged flexible gas connectors, especially older ones.
• Pilot lights that went out on older appliances, allowing gas to escape if the safety does not close.
• Recent work on the appliance or nearby piping.
• Physical damage from moving items in a crowded basement.

When the Smell Is Faint or Brief

Some homeowners notice a brief whiff of gas when a furnace lights, or a faint odor near a gas stove. Even a faint smell can indicate a small leak. The safest approach is to treat any noticeable or persistent gas smell as a leak and call. Gas utilities would rather check a false alarm than miss a real leak.

What If It Smells Like Gas but Might Be Something Else?

Sewer gas from a dry floor drain trap, a dead animal or certain chemicals can sometimes smell similar. But you cannot reliably tell the difference by smell alone. Leave and call first. Once the gas company confirms there is no gas leak, you can investigate other causes, such as refilling a dry floor drain with water.

What Happens When the Gas Company Arrives

A gas utility technician typically checks the air with gas detection equipment, looks for leaks at the meter and service line, and checks inside piping and appliances. If they find a leak in house piping or an appliance, they will usually shut off gas to that appliance or to the building and tag it. That means it must not be used until it is repaired.

The utility generally handles leaks on its side of the meter. Leaks in your home's piping or appliances usually must be repaired by a qualified contractor. In some cases, the utility will need to verify repairs before restoring service.

Getting Your Heat Back Safely

If your furnace, boiler or water heater was shut off because of a leak, call an HVAC contractor or plumber qualified for gas work. They will:

• Locate and repair the leak.
• Pressure test or leak test the repaired piping.
• Inspect the appliance's gas valve and connections.
• Relight and test the appliance.
• Check venting and combustion, including carbon monoxide.

Do not try to relight an appliance yourself after a gas company shutoff. In winter, ask the contractor to prioritize restoring heat, and use only safe temporary heat while you wait. See our guide on space heater safety.

Gas Leaks and Carbon Monoxide Are Different

A gas leak is unburned natural gas escaping, which you can usually smell. Carbon monoxide is produced by burning fuel and has no smell. Both are dangerous. Working carbon monoxide alarms are essential because you cannot smell CO. Some combination alarms also detect natural gas, but they are not required in every home. Our carbon monoxide safety guide explains the difference.

Gas Leaks in Multi-Unit Buildings

In Chicago two-flats, three-flats and apartment buildings, gas piping may serve several units, and meters may be in a shared basement. If you smell gas in a common area or your unit, leave and alert other residents only if you can do so on your way out without delay, for example by knocking on doors as you exit. Do not use the building's intercom or doorbells. Call from outside and let the gas company coordinate.

Preventing Gas Leaks

• Schedule annual furnace, boiler and water heater service, which includes checking gas connections.
• Replace old flexible appliance connectors, especially uncoated brass ones, with modern approved connectors installed by a professional.
• Keep the area around gas appliances clear so pipes and connectors are not bumped.
• Do not hang items on gas pipes.
• Have any new gas appliance or piping installed by a qualified professional with permits.
• Call before you dig outdoors to avoid damaging buried gas lines.

Our fall furnace checklist includes safety steps.

Teach Everyone in the Home

Make sure everyone in your household, including children old enough to understand and any caregivers or tenants, knows what natural gas smells like and what to do: get out, do not touch switches, and call from outside. A plan everyone knows is far more effective than one person knowing what to do.

After the Emergency

Once the leak is repaired and the gas company or contractor has cleared the appliance, have your furnace or boiler fully inspected if it has not been serviced recently. If your heating equipment is old and the leak was in the appliance itself, it may be time to consider replacement. Our guide on how long furnaces last can help.

Other Places Gas Leaks Happen

The furnace area is common, but gas can leak elsewhere too: at the range or cooktop connection, behind a gas dryer, at a gas fireplace, at the water heater, at the gas meter or along buried service lines outside. Outdoors, signs of a leak can include a hissing sound, dead or discolored vegetation over a buried line, or bubbles in standing water. The same rules apply: get away from the area and call from a safe distance.

After a Leak: Questions to Ask

• Where exactly was the leak, and what caused it?
• Was it in the utility's equipment or the home's piping or appliances?
• Has the repair been leak tested?
• Is the appliance safe to use, and has combustion been tested?
• Are other gas connections in the home in similar condition?
• Do I need any permits or inspections for the repair?

Keep the repair documentation with your home records.

Gas Safety With Older Appliances

Many Chicago homes still have older furnaces, boilers and water heaters with standing pilot lights. If a pilot goes out on a modern appliance with a working safety valve, gas should shut off automatically. On very old equipment, or if a safety device has failed, gas could escape. If you notice a gas smell and find a pilot out, do not try to relight it. Leave, call the gas company, and have a technician inspect the appliance afterward. If your equipment is old enough to raise these concerns, it may be time to consider replacement.

Natural Gas Detectors

Some homeowners add explosive gas detectors, or combination CO and gas detectors, near gas appliances for extra warning. They are not a replacement for your sense of smell or for carbon monoxide alarms, and they need to be installed and maintained according to the manufacturer's instructions. If one alarms, treat it like smelling gas: leave and call from outside.

If You Smell Gas Outdoors

A gas smell outside, near the meter or along the street, can mean a leak in the utility's lines. Move away from the area, avoid using anything that could cause a spark, and call Peoples Gas or 911 from a safe distance. Warn others away from the area if you can do so safely. Do not try to operate the gas meter valve yourself.

Gas Smells During or After Construction

Renovations, plumbing work, appliance installations and digging all carry some risk of damaging gas lines. If you smell gas during or after any work in your home or yard, stop the work, get everyone away and call the gas company. Make sure contractors who work on gas piping are qualified and that work is permitted and inspected.

A Quick Summary

• Smell gas: get out.
• Do not touch switches or use phones inside.
• Call Peoples Gas at 866-556-6002 or 911 from outside.
• Do not go back in until cleared.
• Have a qualified contractor repair and test any leak before using appliances again.

Practice the Plan

Like a fire drill, a gas leak plan works best when everyone has practiced it. Agree on a meeting spot outside, decide who will help children, older relatives or pets get out, and make sure everyone knows to call from outside, not inside. In apartment buildings, know the nearest exits and avoid elevators.

Need Gas Appliance Repair?

If the gas company shut off your furnace or boiler, call (312) 638-0812 for furnace repair or boiler repair. We serve neighborhoods including Ravenswood, Belmont Cragin and Wicker Park. If you smell gas right now, leave and call Peoples Gas or 911 first.