Winter Carbon Monoxide Safety: Protect Your Family During Heating Season

Why carbon monoxide is the "silent killer"

Carbon monoxide (CO) is a colorless, odorless gas produced by incomplete combustion in furnaces, water heaters, gas stoves, fireplaces, and attached garages. The CDC reports approximately 420 CO deaths and 100,000 emergency room visits per year in the US. Most incidents occur between November and February when homes are sealed tight and heating equipment runs continuously. Because you cannot see, smell, or taste CO, detector placement and equipment maintenance are your only defenses.

Common sources of CO in your home

• Furnaces — A cracked heat exchanger is the most dangerous source. The crack allows combustion gases to mix with heated air distributed through your ductwork. Annual inspection is the only way to detect this.
• Water heaters — Gas water heaters with blocked or deteriorated flue pipes can backdraft CO into the home. Check the draft diverter during operation — hold a match near it; the flame should pull toward the flue, not push away.
• Fireplaces — Blocked chimneys, closed dampers, or negative pressure from exhaust fans can force CO into living spaces.
• Attached garages — Running a car engine in an attached garage, even with the door open, allows CO to seep into the house through shared walls and ducts.
• Portable generators — Never operate a generator indoors, in a garage, or within 20 feet of any window or vent.

CO detector placement and maintenance

• Install a CO detector on every level of the home, including the basement, and near every sleeping area. Place them at least 15 feet from fuel-burning appliances to avoid false alarms.
• Mount detectors at about 5 feet high on a wall or on the ceiling — CO mixes with air evenly, but placement near breathing height is ideal.
• Test detectors monthly by pressing the test button. Replace batteries annually (or when the low-battery chirp starts).
• Replace the entire detector every 5–7 years. The electrochemical sensor degrades over time and will stop detecting CO even if the unit appears to be working.
• Choose detectors that display a digital ppm (parts per million) readout — they alert you to low-level chronic exposure that basic alarm-only models miss.

Pre-winter maintenance checklist

• Schedule a furnace inspection and tune-up before November ($80–$150). The technician will check the heat exchanger, burner flame color, flue connections, and CO levels at the register.
• Have gas water heaters inspected for proper venting and combustion.
• Get the chimney swept and inspected before the first fire of the season ($150–$350).
• Inspect all flue and vent pipe connections for rust, gaps, or disconnection.
• Ensure the furnace room has adequate combustion air — sealed houses may need a dedicated fresh-air intake.

What to do if your CO detector alarms

If your CO detector alarms with anyone showing symptoms (headache, dizziness, nausea, confusion), evacuate immediately and call 911. If no symptoms are present, open windows, shut off fuel-burning appliances if safe to do so, evacuate, and call your gas utility or fire department. Do not re-enter until professionals have measured CO levels and identified the source. Even low-level exposure (10–70 ppm) over hours causes cumulative health damage — take every alarm seriously.