What Does Carbon Monoxide Smell Like?

Carbon monoxide has no smell. It is an odorless, colorless gas that’s a byproduct of combustion. Because carbon monoxide can leak from your gas furnace, stove, dryer, water heater, wood stove or gas fireplace, it is essential to put safeguards in place for immediate detection when a leak occurs.

To keep your family safe, it’s important to identify all the possible sources of CO in your residence and to properly install and maintain carbon monoxide detectors in your home.

The fact that carbon monoxide has no smell, color, or taste makes it impossible to detect without the right equipment. Every homeowner needs to be aware that this gas is an unseen risk, the exposure to which may prove fatal.

What Is Carbon Monoxide?

Carbon monoxide (CO) is a chemical compound that’s most often created by the combustion of fuels such as wood, gasoline, propane, or charcoal. This compound forms as a gas that’s released along with smoke, carbon dioxide, and other emissions during combustion. Gas appliances and fireplaces are designed to vent the CO they produce outdoors, however, when there’s a malfunction and they leak CO indoors, it causes carbon monoxide poisoning—which can kill if the leak is large enough or if you fall asleep near a smaller leak, like in a basement bedroom positioned near a leaking furnace.

For more guidance on the dangers of carbon monoxide, refer to the CDC’s FAQs.

Symptoms of Carbon Monoxide Poisoning

Symptoms of carbon monoxide poisoning include dizziness, fatigue, headache, and nausea. With high levels of exposure, it may produce vomiting, blurred vision, shortness of breath before inducing loss of consciousness; and occupants may have only minutes to evacuate the house before they fall unconscious and are poisoned to death.

Persons who are asleep at the time of a CO leak will likely not be awoken by these symptoms, elevating the risk of death unless they can rely on an alarm to wake them.

How Is Carbon Monoxide Detected?

Carbon monoxide is a very dangerous and elusive gas to monitor. That’s why homeowners rely on dedicated carbon monoxide detectors placed throughout the home to detect the presence of CO before it can adversely affect their health. It’s important to remember that there is no way to detect CO by yourself. Proper CO detector installation, placement, and maintenance is the only way to keep your home safe.

Carbon monoxide is:

odorless
colorless
tasteless

Carbon Monoxide Sources in the Home

Any combustive element in the home can be a source of carbon monoxide. Some of the most common are:

Fireplace chimneys with obstructed flues
Natural gas-, propane-, or heating oil-fired furnaces
Gas stoves
Gas clothes dryers
Gas water heaters
Automotive exhaust (vehicle accidentally left running in an attached garage, which seeps CO into the home)

To account for the risk of CO from these sources, proper placement of your carbon monoxide detectors is key. Every home should have a CO detector on each floor or level of the house installed five feet or more above the floor. This is because CO is lighter than air, and tends to gather near the ceiling.

Prioritize installing detectors in the same rooms as gas- or wood-fired appliance but keep the detectors at least 10 feet away from them to avoid inaccurate readings.

The proper placement of carbon monoxide detectors is critical to keeping your family safe.

Does Carbon Monoxide Smell Like Rotten Eggs?

No! Some myths surround ways to detect carbon monoxide, such as identifying the strong scent of rotten eggs (like a natural gas leak). Carbon monoxide gas is odorless—it cannot be smelled.

However, never ignore the “rotten egg” smell of natural gas. Try to find the source of the leak (often an unlit gas stove burner accidentally turned on while wiping down the stovetop). Call your gas company or fire dept. if you cannot locate the source of the leak.

Heat Sources, Power Outages and CO Risk

During power outages never use kerosene or gas space heaters indoors to stay warm. They exhaust carbon monoxide directly into the home and will quickly cause carbon monoxide poisoning or death. The same is true for gas-powered generators and gas-powered power tools—neither should ever be used indoors or even in outdoor areas with poor ventilation, like inside or near garages.

What to Do if Carbon Monoxide Is Detected

If you suspect that members of your household are experiencing symptoms of carbon monoxide poisoning or if your detectors alert you, leave your home immediately and contact 911. Emergency services will inspect your home and let you know when it is safe to return.

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