Smoke and CO alarms in Massachusetts homes

Smoke and carbon monoxide alarms are the cheapest safety equipment in a house, and they are also the equipment most often found expired, disconnected or missing. This guide covers how they work, where they usually go and who decides what your home must have.

Two alarms for two dangers

A smoke alarm senses particles from a fire. A carbon monoxide alarm senses CO, a gas with no color and no smell that comes from burning fuel: a furnace, a boiler, a gas stove, a fireplace or a car running in an attached garage. One does not replace the other. Combination units that do both jobs exist.

Smoke alarms use one of two sensing methods. Photoelectric sensors respond best to slow, smoky fires. Ionization sensors respond best to fast, flaming fires, and they are also the ones more likely to go off when you cook. Massachusetts has its own rules about which type may be installed near kitchens and bathrooms.

Battery, hardwired and interconnected

• Battery alarms run on their own. Many newer ones have a sealed battery made to last the life of the alarm.
• Hardwired alarms are connected to the house wiring and have a backup battery for power cuts.
• Interconnected alarms talk to each other. When one senses smoke, they all sound, so a fire in the basement wakes someone on the top floor. The connection can be a wire between the alarms or a wireless signal.

Where alarms usually go

Fire safety organizations give the same general advice: a smoke alarm on every level of the home, including the basement, one outside each sleeping area and one inside each bedroom. CO alarms go on every level and near the bedrooms. On a ceiling, an alarm should sit away from the corners. Keep it away from bathroom doors, cooking appliances and air vents, which cause false alarms or blow smoke away from the sensor.

What Massachusetts requires

Massachusetts requires smoke alarms and carbon monoxide alarms in homes, but the details are not the same for every house. They depend on when the house was built and on whether it has been renovated since. A newer home is expected to have hardwired, interconnected alarms. An older one may be allowed battery alarms.

When a home is sold, the local fire department inspects the alarms before the closing. If you are selling, call your fire department early to ask what they will look for, because a failed inspection can delay the sale.

I do not repeat the rules here, because they are detailed and they change. The Massachusetts Department of Fire Services publishes a guide for homeowners, and your local fire department is the authority for your address.

Alarms expire

The sensor inside an alarm wears out. Smoke alarms should be replaced ten years after the date of manufacture, which is printed on the back or the side of the unit. CO alarms often have a shorter life, stated by the manufacturer, and many sound an end-of-life signal when it is time. An alarm with no date on it is old enough to replace.

A single chirp every minute or so usually means a low battery, or an alarm that has reached the end of its life.

What you can safely check yourself

• Press the test button on every alarm once a month.
• Read the date on each alarm and write down the ones that are close to ten years old.
• Change replaceable batteries when the alarm chirps, or once a year.
• Vacuum the vents of each alarm gently. Dust causes false alarms.
• Count what you have: a smoke alarm on every level and near every bedroom, and CO alarms too.
• A battery alarm is one you can replace yourself, with only a screwdriver. Ask your fire department which type to buy.

When to stop and call an electrician

• Hardwired alarms need replacing and the new ones do not fit the old connector. Do not cut and splice the wires yourself.
• Interconnected alarms all go off and you cannot tell which one started it.
• You want to add alarms to an interconnected system or move from battery alarms to hardwired ones.
• An alarm hangs from its wires or was taken down and never put back.

One more rule that comes before all of these. If a CO alarm sounds, or a smoke alarm sounds and you do not know why, get everyone out of the house and call 911 from outside. Do not look for the cause first.

I install and replace hardwired, interconnected alarms. See smoke and CO detectors or ask for a free quote.