Carbon Monoxide Alarms: Where to Put Them and What to Do

Any fuel that burns can make it.

Carbon monoxide (CO) is a colorless, odorless, poisonous gas produced when fuels burn incompletely: coal, wood, charcoal, oil, kerosene, propane, and natural gas, and engines in generators, cars, lawn mowers, and power washers. The U.S. Fire Administration, citing CPSC, says more than 150 people in the United States die every year from accidental non-fire CO. It happens when a furnace, heater, generator, or other fuel-burning appliance is not working or vented properly.

Without the fever.

CPSC lists early symptoms of low to moderate CO poisoning: headache, fatigue, shortness of breath, nausea, and dizziness. Higher levels bring mental confusion, vomiting, loss of muscle coordination, loss of consciousness, and death. Slow residential leaks are mistaken for the flu, sometimes fatally. Fast, high exposures — a generator running indoors, for example — can confuse and incapacitate people without milder symptoms first. If you think you have symptoms and no alarm has sounded, CPSC says to get outside to fresh air immediately, call the fire department from a neighbor’s home, and see a doctor.

Every level, outside sleeping areas.

• Every level of the home, and outside sleeping areas; USFA says a central location outside each separate sleeping area.
• Not in attics or basements unless they include a sleeping area.
• Not in kitchens or above fuel-burning appliances, and not near heating vents.
• Where nothing covers them: furniture and drapes can block the sensor.
• Plug-in alarms or units mounted high on the wall both work; follow the manufacturer’s instructions.

CPSC recommends battery-operated alarms or alarms with battery backup, so they work in a power outage, interconnected so that when one sounds they all do, and meeting the current UL 2034 standard. Combination smoke and CO alarms are available. Many states and cities require CO alarms; check with your local building code official.

The test button checks the circuit, not the sensor.

CPSC recommends testing alarms every month and replacing batteries at least once a year, or installing alarms with sealed 10-year batteries. Its caution about testing: the test button confirms the circuitry works, not the accuracy of the sensor. CO alarms also have a recommended replacement age, printed in the product literature or available from the manufacturer; write the install date on the alarm. For chirping that is not an alarm, see why an alarm chirps.

Do not try to find the source.

1. Move everyone outside to fresh air immediately.
2. Call 911, the fire department, or your emergency services.
3. Count heads to make sure everyone is out.
4. Do not go back in until emergency responders say you can.

If a malfunctioning appliance was the source, do not use it until trained personnel have serviced it. CPSC says that if the alarm sounds again within 24 hours after you return, repeat the steps and have a qualified technician inspect all fuel-burning equipment. Modern alarms are designed to sound before CO reaches life-threatening levels and are less prone to nuisance alarms than earlier models, so treat every alarm as real.

An alarm is the backup, not the plan.

• Have fuel-burning heating systems, chimneys, and flues professionally inspected every year.
• Run portable generators outdoors only, at least 20 feet from the home with the exhaust pointed away, never in a home, basement, shed, or garage; see generator safety.
• Never leave a car running in an attached garage, even with the door open.
• Never use gas ranges, ovens, or clothes dryers to heat the home, and never burn charcoal indoors.
• Keep vents for the dryer, furnace, stove, and fireplace clear of snow and debris.
• Do not cover the bottom of a gas oven with aluminum foil, which blocks combustion air.

CPSC is clear that a CO alarm is no substitute for the proper use and upkeep of appliances that can produce CO.