People generally associate carbon monoxide poisoning with burning fossil fuels such as oil and gas. But a buildup of creosote in a chimney from wood-burning stoves and fireplaces also increases the risk of this toxic gas backing up into your home. If you're worried about the risk of carbon monoxide poisoning, knowing how to spot a problem, as well as hiring a certified chimney professional to inspect and clean your chimney at least once each year, can help keep you and your family safe.

How Carbon Monoxide Affects the Body

Because carbon monoxide binds easily to hemoglobin in the blood (the molecules that transport oxygen), inhaling high levels of the gas reduces the amount of oxygen getting to the heart, brain, and nervous system. Consequently, severe carbon monoxide poisoning can lead to unconsciousness or even death after just a few minutes. While low level exposure can cause nausea, fatigue, and headaches, exposure to low levels of carbon monoxide over time may lead to additional neurological symptoms including dizziness, coordination problems, confusion, and impaired judgment.

Chimneys Vent By-Products of Combustion

Unless carbon monoxide fumes are properly ventilated out of your home after being released into the chimney, they can pose a serious threat to the members in your household. Incomplete combustion of carbon-containing fuels, including oil, natural gas, wood, and coal, can cause creosote buildup and lead to carbon monoxide gas entering your home.

Like carbon dioxide, smoke, water, and carbon monoxide, creosote is a by-product of combustion when you burn fuel. While the purpose of a chimney is to vent these substances from your home, creosote that doesn't remain in the form of a gas as it goes up the chimney condenses into a liquid that sticks to the inside of the chimney flue. Condensation occurs when flue gases cool before they reach the top of the chimney and are expelled into the air outside.

Signs of Carbon Entering Your Home

When incomplete combustion of a fuel occurs, carbon monoxide rather than carbon dioxide is the by-product produced. There are signs to watch for that may indicate a potential problem.

  • Black, sooty marks on walls, particularly around stoves, fireplaces, and furnaces

  • A gas appliance that burns orange or yellow flames instead of blue flames

  • Excess condensation on windows or moisture collecting on walls or other cold surfaces inside the home

  • Discolored bricks at the top of the chimney

  • Rust on the chimney flue

  • Smoke entering your home because of a faulty flue

What You Can Do

Because carbon monoxide is a colorless and odorless gas, you don't know it's there. That's why it's important to take steps to prevent exposure to carbon monoxide gas.

  1. Provide adequate ventilation in your home. Without enough moving air, carbon monoxide gas can quickly build to dangerous levels.

  2. Install an insulated flue inside your chimney to keep more creosote in a gaseous form, thus limiting the amount of condensation in the flue.

  3. Build smaller fires in a stove that will burn hotter. More of the fuel source will burn completely and produce less smoke.

  4. Have a professional chimney sweep check your chimney for blockage and debris, which can lead to a carbon monoxide leak in your home. Visit websites like to contact professional chimney cleaners.