What causes carbon monoxide in a house

Overview

Carbon monoxide (CO) is often referred to as the "silent killer" because it is an odorless, colorless, and tasteless gas. Its danger lies in its insidious nature; it can build up to dangerous levels in a home without occupants being aware of its presence. The primary culprit behind carbon monoxide in a house is the incomplete combustion of carbon-based fuels. This process occurs when fuels like natural gas, propane, oil, wood, and even charcoal do not burn completely, typically due to a lack of sufficient oxygen.

Common Sources of Carbon Monoxide

Several common household appliances and activities can produce carbon monoxide. Understanding these sources is the first step in preventing CO poisoning.

Fuel-Burning Appliances

The vast majority of indoor CO is generated by fuel-burning appliances. These include:

• Furnaces and Boilers: Gas, oil, or propane furnaces and boilers used for heating are significant potential sources. If the heat exchanger cracks or if the venting system is blocked or leaking, CO can escape into the living space.
• Water Heaters: Similar to furnaces, gas or propane water heaters can produce CO. Proper ventilation and regular maintenance are crucial.
• Gas Stoves and Ovens: While primarily designed for cooking, gas stoves and ovens can release CO, especially if used for extended periods or if there are issues with their ventilation. It's advised not to use a gas oven for heating a room.
• Fireplaces and Wood Stoves: Burning wood in fireplaces or wood stoves can produce CO. A blocked chimney or improper draft can cause smoke and CO to back up into the house. Ensure the damper is open when the fire is lit and for some time after it has died down.
• Gas or Kerosene Heaters: Portable heaters that use gas or kerosene are particularly risky if not used in a well-ventilated area or if they malfunction. Many newer models have safety features to shut them off if oxygen levels drop, but older or poorly maintained units can be dangerous.
• Clothes Dryers: Gas-powered clothes dryers can also be a source of CO if not properly vented to the outside.

Other Sources

Beyond typical home appliances, other activities can contribute to carbon monoxide buildup:

• Attached Garages: Cars, motorcycles, lawnmowers, snow blowers, and other gasoline-powered equipment produce CO when running. If a garage is attached to the house and the door is left open while the engine is running, or if there are any gaps or leaks in the walls or doors connecting the garage to the house, CO can easily enter the living space. Never run a vehicle in an attached garage, even with the door open.
• Generators: Portable generators, especially when used during power outages, are a major cause of CO poisoning. They should always be operated outdoors, far away from windows, doors, and vents.
• Blocked Chimneys and Vents: Anything that obstructs the exhaust path of fuel-burning appliances can cause CO to accumulate indoors. This includes bird nests, snow, ice, debris, or even collapsed ductwork.
• Improper Installation or Maintenance: Appliances that are not installed according to manufacturer instructions or local building codes, or that are not regularly maintained, are more likely to produce and release CO.

Why Incomplete Combustion Happens

Complete combustion occurs when a fuel reacts with sufficient oxygen to produce carbon dioxide (CO2) and water. However, when oxygen is limited, the combustion process is incomplete, and carbon monoxide (CO) is produced instead. This can happen due to:

• Poor Ventilation: The most common reason for insufficient oxygen. If an appliance is installed in a sealed-off space or if vents are closed or blocked, it won't get enough air to burn fuel completely.
• Appliance Malfunction: Internal problems with an appliance, such as a cracked heat exchanger in a furnace, can disrupt the combustion process and allow CO to escape.
• Blocked Flues or Chimneys: If the exhaust pathway is blocked, the byproducts of combustion, including CO, cannot escape outside and may be forced back into the home.

Health Risks of Carbon Monoxide

Carbon monoxide poisoning can cause flu-like symptoms such as headaches, dizziness, nausea, vomiting, confusion, and fatigue. At higher concentrations, it can lead to loss of consciousness, brain damage, and death. Individuals with heart disease, respiratory problems, anemia, and the elderly and young children are particularly vulnerable.

Prevention and Detection

The best defense against carbon monoxide is prevention and detection. Ensure all fuel-burning appliances are professionally installed, regularly inspected, and maintained. Keep chimneys and vents clear of obstructions. Install battery-operated or plug-in CO alarms with battery backup on every level of your home and outside sleeping areas. Test these alarms monthly and replace them according to the manufacturer's instructions (typically every 5-10 years).