Gas Smell or Carbon Monoxide Alarm Near Your Fireplace

If you smell gas: leave first

Do these in order. Don't stop to find the source, and don't try to fix anything.

• Get everyone out now, pets included. Don't stop to open windows; Massachusetts guidance and National Grid both say to leave windows as they are.
• Don't flip light switches, unplug anything, ring a doorbell or use any phone inside the home. A spark can ignite gas.
• Don't light a match, smoke, or try to light or turn off the fireplace. Massachusetts guidance says not to try to shut off the gas yourself.
• Don't start a car in the garage or next to the house. Eversource warns that a spark from a car could ignite gas.
• Once you are outside and well away from the building, call 911 or your gas company's emergency number listed below. If you don't know your gas company, call 911.
• Wait outside. Don't go back in until the fire department or the gas company tells you it is safe.

If a carbon monoxide alarm sounds

Carbon monoxide is poisonous, with no color, smell or taste, so treat every alarm as real. The first three steps below come from the Massachusetts Department of Fire Services.

• Get everyone out of the house and into fresh air.
• Call 911 or the fire department from outside, using a cell phone or a neighbor's phone.
• If anyone has a headache, nausea, dizziness or confusion, or feels like they have the flu, get medical help right away.
• Leave the fireplace and other appliances alone, and don't go back in until responders say it is safe.

Gas company emergency numbers in Greater Boston

The Massachusetts Department of Public Utilities lists the gas company for each city and town. In the 68 towns we serve, it lists National Grid, Eversource and the Wakefield Municipal Gas & Light Department, and Eversource uses two numbers depending on the area.

The company's name is on your gas bill. Some towns are served by more than one company, and gas isn't available at every address, so check the bill when you can. In an emergency, 911 works everywhere.

• National Grid: 1-800-233-5325. The state list shows National Grid in most of the towns we serve, including Boston, Newton, Quincy and Melrose.
• Eversource, former NSTAR Gas area: 800-592-2000. The state list shows it in Cambridge, Dedham, Framingham, Needham, Sherborn and Westwood, and alongside National Grid in Boston, Natick, Somerville and Wayland.
• Eversource Gas Company of Massachusetts, formerly Columbia Gas: 800-525-8222. The state list shows it in Andover, Canton, Dover, North Andover and Norwell.
• Wakefield Municipal Gas & Light Department: 781-246-6363. The state list shows it, along with National Grid, in Wakefield.
• Eversource asks callers to dial 911 first and then report the leak to the company. Its website also shows the right number when you enter your town.

Is it gas, or another smell?

Natural gas has no smell of its own. Gas companies are required to add an odor so you can notice a leak; Eversource describes a rotten egg-like smell, and National Grid calls its additive sulfur-smelling.

Fireplaces can give off other smells. Valor's H4 homeowner's manual says a new fireplace can have a slight odor for its first few hours as curing compounds burn off. Our guide to starting a gas fireplace after summer covers smells you may notice on the first fire of the season.

If you aren't sure which smell it is, treat it as gas: leave, and call from outside. National Grid also asks people not to assume someone else has already reported a leak.

Massachusetts carbon monoxide alarm rules

The Massachusetts Department of Fire Services says every home must have working smoke alarms and most homes must also have carbon monoxide alarms. Its guidance on carbon monoxide alarms covers these points.

• The law requires CO alarms on every level of the home, including habitable parts of basements and attics, in most homes.
• On levels with bedrooms, CO alarms should be within 10 feet of the bedroom doors.
• Accepted types are battery alarms with battery monitoring, plug-ins with battery backup, low-voltage systems, wireless alarms and qualified combination alarms.
• Replace CO alarms every 5 to 7 years, depending on the make and model. Newer alarms with a 10-year sealed battery are replaced as a whole unit at 10 years.
• The battery in a plug-in alarm can run down during a long power outage and may need replacing.
• State law also requires landlords to install and maintain CO alarms in every unit that has a source of carbon monoxide.
• Choose alarms listed by a national testing lab such as UL or Intertek (ETL).

After the emergency

Don't use the fireplace again until the fire department or the gas company has cleared the home and a qualified technician has checked it. The Department of Fire Services advises having fuel-burning appliances inspected every year before the heating season, and checking vent pipes, flues and chimneys for leaks or blockages.

We are not an emergency line. For a gas smell or a CO alarm, always call 911 or your gas company first.

Once responders say the home is safe, a licensed Massachusetts gas fitter can check the fireplace with our $99 gas fireplace safety inspection, which includes a gas leak check, a wiring and controls check and a safety check. If the fireplace needs work, our gas fireplace repair page explains what that can involve, and you can request a visit online.

Problems that aren't emergencies, like a fireplace that keeps turning off or a pilot that won't stay lit, have their own pages.