Carbon monoxide

Carbon monoxide comes from burning fuel. It is produced any time you burn fuels such as wood, charcoal, natural gas, gasoline or heating oil. It interferes with the delivery of oxygen through the body. Many household items, including gas- and oil-burning furnaces, portable generators and charcoal grills, produce it.

Any fuel-burning appliance can be a source, especially one without enough ventilation or one that is installed, maintained or used improperly. Worn or poorly adjusted boilers and furnaces can be significant sources, and so can a flue that is the wrong size, blocked, disconnected or leaking. CO can escape from faulty furnaces or room heaters, or through rusty or cracked vents. It can also be trapped inside a home by a blocked chimney flue.

It is not only a winter problem. The Illinois Department of Public Health says unintentional CO exposures are most common in the cold months from October to March, but they can and do happen at any time of year. Its report found that CO exposures led to an average of 940 emergency department visits, 126 hospital admissions and nearly 57 deaths a year in Illinois over the five years it studied.

Source: City of Chicago · U.S. EPA · CDC · U.S. Consumer Product Safety Commission · Illinois Department of Public Health

Carbon monoxide poisoning is easy to mistake for something else. The most common symptoms are headache, dizziness, weakness, upset stomach, vomiting, chest pain and confusion. The first symptoms of low to moderate poisoning are like the flu, but without the fever. When CO builds up slowly at home, people and even doctors can mistake mild to moderate poisoning for the flu, which sometimes ends in tragic deaths.

How sick a person gets depends on both the CO level and how long they breathe it. High-level poisoning brings more and more severe symptoms, including mental confusion, vomiting, loss of coordination, loss of consciousness and, finally, death. Breathing in a lot of CO can make you pass out or kill you. This is why the safety steps at the end of this page matter.

Some people are more sensitive than others. Unborn babies, infants, elderly people and people with anemia or a history of heart or breathing disease can be especially sensitive to carbon monoxide. The type, severity and timing of effects can vary a lot with each person's age, overall health, length of exposure and the amount of CO. In a home with a baby or an older relative, a working alarm matters even more.

Source: CDC · U.S. Consumer Product Safety Commission · U.S. EPA

CO alarms are a legal requirement in most homes. As of January 1, 2007, Illinois requires homeowners, landlords and building owners to install carbon monoxide detectors within 15 feet of rooms used for sleeping. The state law is enforced by the local authority, which may also enforce its own additional requirements. An approved alarm must meet the State Fire Marshal's rules, carry the label of a nationally recognized testing laboratory and meet the latest Underwriters Laboratories or Canadian Standards Association standards.

Chicago spells out the rules for the city. Carbon monoxide alarms are required by law in all residential buildings in Chicago where there is a risk of carbon monoxide poisoning. In those homes, an alarm must be installed within 15 feet of any bedroom. An alarm must also be installed inside any bedroom that has a fuel-burning appliance or fireplace. Alarms must be made to meet the UL 2034 standard.

Some homes are exempt. In Chicago, alarms are not required in homes without these risk factors, such as a home or apartment with all-electric heating and appliances and no attached garage. Illinois law exempts a unit in a building that does not burn fossil fuel for heat, ventilation or hot water, is not connected to a garage, and is not close enough to a vented source of CO to receive it, as the local building commissioner determines.

Source: Illinois State Fire Marshal · Illinois General Assembly · City of Chicago

The law splits the work between building owners and the people living there. In Chicago, building owners must provide required CO alarms and replace them if they fail, malfunction or reach the end of their service life. Owners must also tell occupants in writing about their duty to test and maintain the alarms in their homes. Owners face fines of $500 to $2,000 per day, per violation, if they do not provide working alarms where required, whatever the reason.

Occupants have their own part. In Chicago, occupants must provide and keep working batteries in alarms that run entirely on removable batteries or need a removable backup battery. They must test the alarms regularly, and if one is not working, they must promptly tell the building owner in writing. Under Illinois law, tampering with, removing, disconnecting or taking the batteries out of an installed alarm, except during inspection, maintenance or replacement, is a Class A misdemeanor for a first conviction and a Class 4 felony after that.

Source: City of Chicago · Illinois General Assembly

Alarms come in a few kinds, and newer buildings have stricter rules. Illinois allows a CO detector that runs on batteries, plugs in with a battery backup, or is wired into the home's power with a battery backup. In Chicago, alarms in houses and apartments built since 2018 must be connected to the building's power (hardwired) and must also have a removable backup battery. Alarms in houses and apartments built before 2018 may run on a removable battery.

You can also combine alarms. Chicago allows devices that combine smoke and carbon monoxide alarms or that connect with your smoke alarms, but does not require them. Illinois law lets a combined unit be used only if it meets the rules for both kinds of alarm and its alarm clearly tells the two apart. The CPSC says interconnected CO alarms are best, because when one sounds, they all sound.

Source: Illinois State Fire Marshal · City of Chicago · Illinois General Assembly · U.S. Consumer Product Safety Commission

Where an alarm goes matters as much as having one. Chicago says to put CO alarms on a wall at least 5 feet above the floor or on the ceiling, because CO is slightly lighter than air and often mixes with warm, rising air. Do not install one right next to or over a fireplace, stove or other appliance with an open flame. The State Fire Marshal also says not to install a detector near your kitchen or garage, or in a room with a furnace.

Federal agencies add guidance for the rest of the house. The CPSC says to install alarms on every level of the home and outside sleeping areas. The EPA suggests a central spot on every level of the living space, including the basement, at least 15 feet from any fuel-burning appliance. Follow the manufacturer's instructions and all laws and building codes for where alarms go and how often to replace them.

Source: City of Chicago · Illinois State Fire Marshal · U.S. Consumer Product Safety Commission · U.S. EPA

An alarm only helps if it works. Test your CO alarms often and replace dead batteries. Chicago says to replace the batteries every year or as often as the manufacturer recommends. The CDC suggests checking the batteries when you change your clocks each spring and fall.

Alarms wear out too. Chicago says to replace the whole alarm when it reaches its expiration date, every 5 to 10 years. The CDC says to replace it following the manufacturer's instructions or every 5 years. The Illinois Department of Public Health calls regular testing, checking expiration dates and replacing broken or outdated units your strongest defense against accidental CO poisoning.

Take every alarm seriously. Alarms are designed to sound before most people feel symptoms. No detector is 100% reliable, and some people can have health problems at CO levels below what these devices detect. So an alarm works alongside yearly service, not instead of it: have your heating system, chimneys and vents inspected and serviced every year by a trained technician.

Source: U.S. Consumer Product Safety Commission · City of Chicago · CDC · Illinois Department of Public Health · U.S. EPA