Furnaces, boilers and carbon monoxide: how to keep your home safe

Updated November 10, 2026 · KeystoneProGuide editorial team

Can a furnace or boiler cause carbon monoxide poisoning?

Yes. The Centers for Disease Control and Prevention (CDC) says gas- and oil-burning furnaces produce carbon monoxide, an invisible, odorless gas that kills without warning. The U.S. Consumer Product Safety Commission (CPSC) says carbon monoxide comes from the incomplete burning of fuels including natural gas, propane, oil and kerosene, and that heating equipment is among the top contributors to deaths from it.

The numbers are large enough to take seriously. The CDC estimates that each year more than 400 Americans die from unintentional carbon monoxide poisoning not linked to fires, more than 100,000 visit an emergency department and more than 14,000 are hospitalized. The CPSC's narrower count, deaths linked to consumer products, is more than 200 a year.

How does heating equipment produce it?

When something about the burning or the venting goes wrong. The U.S. Environmental Protection Agency (EPA) lists the household sources, and several are heating faults:

• leaking chimneys and furnaces;
• back-drafting from furnaces, gas water heaters, wood stoves and fireplaces;
• worn or poorly adjusted and maintained furnaces and boilers;
• a flue that is improperly sized, blocked, disconnected or leaking.

ENERGY STAR's maintenance checklist explains the equipment side: a dirty burner or a cracked heat exchanger makes the burner operate improperly, and faulty gas or oil connections are a fire hazard and can contribute to health problems.

What are the symptoms?

The CPSC says early symptoms of low to moderate exposure are like the flu without the fever: headache, fatigue, shortness of breath, nausea and dizziness. Higher levels bring confusion, vomiting, loss of coordination and loss of consciousness. The CDC's list adds weakness, chest pain and upset stomach, and the EPA notes symptoms that clear up after you leave home, which is a useful clue.

Two warnings stand out. The CPSC says slowly developing problems at home are sometimes mistaken for flu, by families and by doctors. And the CDC says people who are sleeping, drunk or under the influence can die before they have symptoms. It names infants, the elderly and people with chronic heart disease, anemia or breathing problems as more likely to get sick.

Where should carbon monoxide alarms go?

The agencies agree on the basics:

• On every level of the home and outside sleeping areas, says the CPSC, using battery-operated alarms or alarms with battery backup. Interconnected alarms are best, because when one sounds they all sound.
• Not in the kitchen, not directly above fuel-burning appliances, and not near heating vents, where the CPSC says alarms do not belong, and not where furniture or curtains could cover them.
• To a current standard. The CPSC says to choose an alarm that meets UL 2034.

Keep them working. The CDC suggests checking batteries when the clocks change in spring and fall and replacing alarms as the maker directs or every 5 years. The CPSC notes that the test button checks the circuitry, not the sensor, and that newer alarms give an end-of-life signal. Many states and towns require alarms in homes; the CPSC says to check with your local building code official.

An alarm is a backstop. The CPSC says it provides some added protection but is no substitute for proper use and upkeep of the appliances themselves.

What should you do when the alarm goes off?

Get out, then call. The CPSC's steps:

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

If the cause is a malfunctioning appliance, do not run it again until trained personnel have serviced it. If the alarm sounds again within 24 hours of returning, the CPSC says to repeat the steps and have a qualified technician check every fuel-burning appliance.

If you also smell gas, follow your gas utility's instructions. Philadelphia Gas Works, for example, says to leave immediately and call its emergency line from a safe location, without using phones or other electrical devices nearby.

What should the yearly inspection cover?

All three agencies recommend one. The CPSC urges a yearly professional inspection of every fuel-burning heating system, including furnaces, boilers, water heaters, chimneys, flues and vents. It says the inspector should check chimneys and flues for blockages, corrosion, and partial or complete disconnections and loose connections. The EPA says to have a trained professional inspect, clean and tune up the furnace, flues and chimneys annually and to repair leaks promptly. The CDC says to have the heating system, the water heater and any other gas, oil or coal burning appliance serviced every year.

At home, the CDC adds that horizontal vent pipes on appliances such as water heaters should rise slightly toward the outdoors, which helps prevent leaks at loose joints.

What habits cause trouble?

• Heating with the oven or range. The CPSC and CDC both say never to use gas cooking appliances to heat a home.
• Blocking vents during renovations. The CPSC says to make sure vents and chimneys are not covered by tarps or debris.
• Do-it-yourself burner work. The CPSC says never to service fuel-burning appliances without the proper knowledge, skill and tools.
• Generators too close to the house. The CPSC says at least 20 feet away, outdoors only, with the exhaust pointed away.

Is help available for low-income households?

Pennsylvania's Weatherization Assistance Program includes health and safety work: testing and repairing heating system safety features and installing carbon monoxide alarms, for households that qualify. And for those weighing a change of system, ENERGY STAR notes that heat pumps involve no combustion, so they produce no carbon monoxide themselves.

How often to book the inspection is in how often to service your HVAC system, and what to do about other urgent signs is in signs your system needs a professional. Contractors are listed on the HVAC contractors directory page.

Sources

1. Carbon Monoxide (CO) Poisoning Basics, Centers for Disease Control and Prevention
2. Furnace Safety Fact Sheet, Centers for Disease Control and Prevention
3. Carbon Monoxide Fact Sheet, U.S. Consumer Product Safety Commission
4. Home Heating Equipment, U.S. Consumer Product Safety Commission
5. Carbon Monoxide, U.S. Consumer Product Safety Commission
6. Carbon Monoxide's Impact on Indoor Air Quality, U.S. Environmental Protection Agency
7. Maintenance Checklist, ENERGY STAR
8. Air-Source Heat Pumps, ENERGY STAR
9. Natural Gas Safety, Philadelphia Gas Works (PGW)
10. Weatherization in PA, Pennsylvania Department of Community and Economic Development