Around 1,500 people die annually due to accidental carbon monoxide exposure, and an additional 10,000 seek medical attention. Carbon monoxide can escape from any fuel-burning appliance, furnace, water heater, fireplace, wood burning stove, or space heater. Most newer homes are built extremely air-tight, thus cutting down on the supply of fresh air to your furnace creating an oxygen starved flame. Tight closing replacement windows and doors, as well as additional insulation can cause similar problems in older homes. When this condition occurs unsafe levels of carbon monoxide may be produced.
Carbon monoxide can spill from vent connections in poorly maintained or blocked chimneys.
If the flue liner is cracked or deteriorated, carbon monoxide can seep through the liner and into the house - slowly creeping up to dangerous levels. If a nest or other material restrict or block the flue of the chimney, carbon monoxide will spill back into the house. Improperly sized flues connected to new, high-efficiency furnaces and water heaters can also contribute to carbon monoxide spillage. Many new furnaces and water heaters are installed using the existing chimneys which may be the wrong size to allow the furnace to vent properly. Carbon monoxide inhibits the blood's capacity to carry oxygen.