Why Carbon Monoxide Levels Spike in Winter
Carbon monoxide (CO) problems increase dramatically during the winter months. As homes seal up tightly and heating systems run longer, small issues that go unnoticed in warmer seasons can suddenly become dangerous.
Understanding the causes helps you protect your home and family from this invisible threat.
1. Furnaces Running Longer and Harder
When your furnace runs continuously, any minor combustion issue becomes magnified. A cracked heat exchanger, dirty burners, or improper fuel mixture can all lead to elevated CO levels.
Fix: Schedule annual furnace maintenance and replace filters regularly.
For more heating-related troubleshooting, visit our HVAC category.
2. Blocked or Frozen Exhaust Vents
Snow, ice, or debris can block furnace or water heater exhaust vents, forcing carbon monoxide back into the home.
Fix: Inspect exterior vents after snowstorms and keep them clear year-round.
3. Poor Home Ventilation
Winter weather leads homeowners to close windows, seal drafts, and tighten up airflow. While this improves energy efficiency, it also traps pollutants—including carbon monoxide.
Fix: Ensure your home has proper ventilation, especially in utility rooms and basements.
4. Malfunctioning Gas Appliances
Gas stoves, fireplaces, and water heaters can all produce carbon monoxide if they’re not burning fuel properly.
Fix: Have gas appliances inspected annually and watch for soot buildup or yellow flames.
For more appliance troubleshooting, explore our Appliances category.
5. Running Vehicles in Attached Garages
Even with the garage door open, carbon monoxide can seep into the home through shared walls or gaps.
Fix: Never warm up a vehicle inside an attached garage.
6. Failing or Old Carbon Monoxide Detectors
CO detectors typically last 5–7 years. After that, their sensors become unreliable.
Fix: Replace detectors according to manufacturer guidelines and test them monthly.
See more safety tips in our Home Safety category.
When to Call a Professional
If your CO detector alarms, leave the home immediately and call emergency services. After the home is cleared, schedule an inspection with a licensed HVAC or gas technician.
Before hiring someone, review our General Home Tips category.