Carbon monoxide (CO) is an odorless, colorless gas formed by the incomplete combustion of fuels. When people are exposed to CO gas, the CO molecules will displace the oxygen in their bodies and lead to poisoning.

The problem with CO

Since CO has no odor, color or taste, it cannot be detected by our senses. This means that dangerous concentrations of the gas can build up indoors and humans have no way to detect the problem until they become ill. Furthermore, when people become sick the symptoms are similar to the flu, which can cause victims to ignore the early signs of CO poisoning.

The CDC estimates that approximately 400 people die from unintentional CO exposure in the United States every year. Data specific to Minnesota show that an average of 14 people die due to unintentional CO poisoning each year. Approximately 300 people visit emergency department each year for treatment of symptoms linked to unintentional CO exposure. For more information Carbon Monoxide Data Portal.

The good news is that carbon monoxide poisoning can be prevented with simple actions such as installing a CO alarm and maintaining fuel burning appliances.

Carbon Monoxide sources in the home

CO is produced whenever a material burns. Homes with fuel-burning appliances or attached garages are more likely to have CO problems Common sources of CO in our homes include fuel-burning appliances and devices such as:

Clothes dryers.
Water heaters.
Furnaces or boilers.
Fireplaces, both gas and wood burning.
Gas stoves and ovens.
Motor vehicles.
Grills, generators, power tools, lawn equipment.
Wood stoves.
Tobacco smoke.

Carbon monoxide leaks from appliances can cause poisoning. Detection is required in new construction and when installing boilers and water heaters (under fire and boiler codes).

Group E and I-4 Carbon Monoxide(CO) Detection Flow Chart (PDF) (MN Fire Marshall)
BOILER CODES AND LAWS (MN Department of Labor and Industry)

Typical indoor CO concentrations

Ideally, the level of CO indoors should be the same as CO concentrations outside. In the Minneapolis/St. Paul metro area, outdoor CO levels typically range from 0.03-2.5 parts per million (ppm) averaged over an 8-hour period. These levels are well below the federal standard of 9 ppm for CO in outdoor air. In general, concentrations are lower in rural areas and higher in urban areas. Finding CO concentrations higher indoors than outdoors indicates a source of CO either inside or very close to your home.

CO and recreation

There are a number of ways people can be exposed to high levels of carbon monoxide while participating in activities such as camping, fishing, hunting and boating.

Items such as camp stoves, charcoal grills, fuel-burning lanterns and generators should never be used inside a tent, RV or cabin.
Do not place portable generators near open doors and windows.
Ice fishing houses that use heating equipment should have a working CO alarm installed and users should crack a window for additional ventilation.
Heating equipment in cabins and ice houses should be regularly inspected and be in good condition.
Boaters should be aware of exhaust area at the back of the boat and should tow passengers at least 20 feet from this area.
Be aware of exhaust from neighboring boats when parked near them.
Install a CO alarm in the cabin of boats.

Protecting your family from CO poisoning

1. Properly vent and maintain fuel-burning appliances

It is important to know what appliances in your home are fuel-burning and make sure that they are maintained properly. All of these appliances should be vented to the outside. You should have your fuel-burning appliances (ex. furnace) checked by a qualified heating contractor every year to look for potential problems. It is also a good idea to know the signs of a potential CO problem:

Streaks of soot around fuel-burning appliances, or fallen soot in a fireplace.
Absence of an upward draft in your chimney.
Excess moisture and condensation on windows, walls and cold surfaces.
Rusting on flue pipes or appliance jacks.
Orange or yellow flame in combustion appliances (the flame should be blue).
Damaged or discolored bricks at the top of the chimney.

Never use appliances intended for outdoor use inside. Examples include barbecue grills, camp stoves, portable generators or gas-powered lawn equipment. Do not use an oven to heat your home. Not only is it a fire risk, it is also a carbon monoxide hazard. Do not run or idle your vehicle in an attached garage. Instead, back your vehicle out right away. Check that your vehicle’s exhaust pipe is not blocked, for example, by snow during the winter.

2. Know the symptoms of CO poisoning

Identifying CO poisoning can be difficult because the symptoms are similar to the flu. CO is often called the “silent killer” because people will ignore early signs and eventually lose consciousness and be unable to escape to safety.

For most people, the first signs of exposure include mild headache and breathlessness with moderate exercise. Continued exposure can lead to more severe headaches, dizziness, fatigue and nausea. Eventually symptoms may progress to confusion, irritability, impaired judgment and coordination, and loss of consciousness.

You can tell the difference between CO poisoning and the flu with these clues:

You feel better when you are away from home.
Everyone is the home is sick at the same time (the flu virus usually spreads from person to person).
The family members most affected spend the most time in the house.
Indoor pets appear ill.
You don’t have a fever or body aches, and you don’t have swollen lymph nodes that are common with the flu and some other infections.
Symptoms appear or seem to get worse when using fuel-burning equipment.

3. Install and maintain CO alarms in your home

Minnesota state law (MN Statute 299F.50) requires that every home have at least one operational CO alarm within 10 feet of every room legally used for sleeping. All CO alarms should conform to the latest Underwriters Laboratory (UL) Standards. Please follow the manufacturer’s instructions for placement of your CO alarm, and take note of the suggested replacement date.

Frequently asked questions

Are some people at greater risk of CO poisoning?

Yes, some people are at a greater risk for CO poisoning. Those individuals include people with:

Respiratory conditions, such as asthma or emphysema.
Cardiovascular disease.
Anemia or sickle cell anemia.

Also, the elderly and young children are at a greater risk for CO poisoning than adults. Individuals engaging in strenuous activity have also been found to be at greater risk. Remember, ANYONE can become sick and die from CO poisoning when exposed to very high levels.

Can CO be a problem in the summer?

Yes. Although CO poisoning cases are higher during the winter months, there are situations where people can be exposed to high levels of CO during the summer. Vehicles including boats produce carbon monoxide. Devices such as camp stoves, barbecue grills and non-electric heaters are commonly used during recreational activities and also are sources of CO.

The CDC has noted that CO poisoning cases have resulted from the use of power generators during power outages. Portable generators are capable of producing more carbon monoxide than modern cars and can kill people in a short amount of time. It is recommended that users place generators at least 25 feet away from and downwind of a house. Be sure that there are no vents or openings near the generator that would allow exhaust to enter into your home.

How long do CO alarms last?

The typical lifespan of a CO alarm is between 5 and 7 years, but it varies by manufacturer. Consult the product packaging or manufacturer for a recommended replacement date.

What do I do when my CO alarm sounds?

Don’t ignore a CO alarm if it is sounding. If people in the home are exhibiting symptoms of CO poisoning, immediately leave the building and call your local fire department. In cases where residents are feeling fine, call your local gas utility company or a qualified technician to help identify the cause of the problem.

Indoor Air

Related Topics

Environmental Health Division