If your carbon monoxide alarm is going off or you suspect a leak, get everyone out of the building immediately and call 911 from outside. Do not stay inside to open windows, locate the source, or grab belongings. Carbon monoxide is colorless and odorless, so you cannot tell how much you’ve been breathing in or for how long. In the U.S., an estimated 204 people die each year from accidental, non-fire CO poisoning linked to consumer products.
Immediate Steps During a CO Emergency
Leave the building right away and bring everyone with you, including pets. Move to fresh air, ideally across the street or at least well away from the structure. Once you’re outside, call 911. Do not re-enter the building until emergency responders have cleared it.
If anyone is showing symptoms, tell the 911 dispatcher. CO poisoning symptoms include headache, dizziness, nausea, vomiting, chest pain, weakness, and confusion. They’re often mistaken for the flu, which is one reason CO poisoning is so dangerous. People who are asleep, intoxicated, or sedated can die from CO exposure before they ever notice a symptom.
Account for everyone in the household. If someone has collapsed or can’t move on their own and you can safely reach them, help them outside. If you can’t do so safely, tell the fire department their location as soon as they arrive.
Why Carbon Monoxide Is So Dangerous
Carbon monoxide binds to hemoglobin in your blood roughly 200 times more readily than oxygen does. Once it attaches, it blocks your red blood cells from carrying oxygen to your brain, heart, and other organs. The result is a body-wide oxygen shortage that can cause permanent damage or death, even in otherwise healthy people.
The gas clears from your blood slowly. Breathing normal room air, the amount of CO in your blood drops by half every four hours or more. With pure oxygen delivered through a mask, that drops to 40 to 80 minutes. In a hyperbaric oxygen chamber, where oxygen is delivered under high pressure, it takes roughly 23 minutes. This is why getting to fresh air fast matters so much, and why hospitals use concentrated oxygen as the primary treatment.
What Happens at the Hospital
Emergency teams will give you high-flow oxygen through a mask to flush the carbon monoxide out of your blood as quickly as possible. A blood test measures your carboxyhemoglobin level, which tells doctors how much CO is still bound to your hemoglobin. Levels above 25% are considered severe poisoning.
For more serious cases, doctors may recommend hyperbaric oxygen therapy, where you breathe pure oxygen inside a pressurized chamber. This is most commonly used when someone lost consciousness, showed neurological changes like confusion or difficulty walking, or is pregnant. The treatment works best within the first six hours after exposure. For moderate cases, one session is typically enough. Severe poisoning may require two or three sessions.
Delayed Symptoms After Recovery
One of the more unsettling aspects of CO poisoning is that problems can surface days or even weeks after you seem to have fully recovered. Up to 40% of people with significant exposure develop what doctors call delayed neuropsychiatric syndrome. This can appear anywhere from 3 to 240 days after the initial poisoning.
Symptoms include memory problems, difficulty concentrating, personality changes, depression, anxiety, and in some cases movement disorders like tremors or muscle stiffness. The good news is that 50 to 75% of people recover within a year. Some, however, are left with lasting cognitive or emotional effects. This is one reason doctors sometimes opt for hyperbaric oxygen even in borderline cases: it’s difficult to predict who will develop these delayed problems.
Common Household Sources
Carbon monoxide comes from anything that burns fuel. The most common culprits in homes are gas furnaces, water heaters, gas stoves and ovens, fireplaces, wood stoves, and attached garages where cars idle. Portable generators are a particularly deadly source, responsible for a large share of accidental CO deaths each year, especially during power outages when people run them indoors or in enclosed spaces like garages or basements.
Problems often start with poor maintenance. A cracked heat exchanger in a furnace, a blocked chimney flue, or a malfunctioning gas appliance vent can all send CO directly into your living space. Having fuel-burning appliances inspected annually by a qualified technician is one of the simplest ways to prevent a leak.
CO Detector Placement and Maintenance
Every floor of your home needs its own carbon monoxide detector. If you’re only installing one, place it near the bedrooms and make sure the alarm is loud enough to wake you. Many CO deaths happen at night because people inhale the gas while sleeping and never regain consciousness.
CO detectors don’t last forever. They have a lifespan of about seven years. All detectors manufactured after August 2009 include an end-of-life warning, a chirping pattern that’s different from a low-battery alert. If your detector is chirping and replacing the battery doesn’t stop it, the unit itself has expired and needs to be replaced entirely. If your detectors were installed in 2018 or earlier, check the expiration date printed on the back. An expired detector provides zero protection.
Protecting Pets
Dogs, cats, and especially birds are vulnerable to carbon monoxide, often more so than humans because of their smaller body size and faster breathing rates. Birds in particular can succumb very quickly. If your CO alarm goes off, take your pets outside with you. Signs of CO exposure in animals mirror those in humans: lethargy, unsteadiness, vomiting, and difficulty breathing. A pet that suddenly becomes lethargic or disoriented when the rest of the household also feels unwell is a red flag that CO could be present, especially in a home without a working detector.
Preventing CO Buildup
Most CO emergencies are preventable. A few straightforward habits make a significant difference:
- Never run a generator indoors or in a garage, basement, or crawl space, even with the door open.
- Never use a gas oven or stovetop for heating.
- Never idle a car in an attached garage, even with the garage door raised.
- Schedule annual inspections for your furnace, water heater, and any other gas or fuel-burning appliance.
- Keep vents and chimneys clear of debris, snow, and bird nests.
- Replace CO detectors before they reach their seven-year expiration date.
CO poisoning is almost entirely preventable with working detectors and properly maintained appliances. The gas gives no warning on its own, so your detector is the only thing standing between a small malfunction and a life-threatening emergency.