What causes carbon monoxide? What are some common sources of carbon monoxide?

Carbon monoxide (CO) is a by-product of incomplete combustion. Common causes of carbon monoxide production can be gas or oil appliances like a furnace, clothes dryer, range, oven, water heater, or space heaters that are not working properly. When appliances and vents work properly, and there is enough fresh air in your home to allow for complete combustion. In these typical conditions, trace amounts of CO produced by these sources are typically not dangerous. However, there are common conditions that can cause CO levels to rise quickly:

  • Appliance malfunction, i.e. the heat exchanger on your furnace cracks.
  • Vent, flue, or chimney is blocked by debris or even snow.
  • Fireplace, wood burning stove, charcoal grill or other source of burning material is not properly vented.
  • Vehicle is left running in an attached garage and carbon monoxide seeps into the house.
  • Several appliances running at the same time and competing for limited fresh air can be a cause of carbon monoxide build-up. This condition can result in incomplete combustion and produce CO, even if all appliances are in good working condition.