If you suspect carbon monoxide in your home, get everyone outside immediately and call 911. Do not stay inside to search for the source, open windows, or gather belongings. Every minute of continued exposure increases the risk of serious harm. Once you’re outside in fresh air, call emergency services and do not go back inside until responders confirm it’s safe.
Get Out First, Then Call for Help
The single most important action is leaving the building. Carbon monoxide is colorless and odorless, so you cannot gauge how much you’ve already inhaled. If your CO detector is sounding or multiple people in the household feel sick at the same time, treat it as an emergency and move outside right away.
If you physically cannot get outside, open a window or door and position yourself directly next to it so you’re breathing outdoor air. Call 911 from that spot. Once outside, account for every person and pet in the household. Do not reenter the home for any reason until fire department personnel or emergency responders clear you to do so.
Symptoms That Should Raise Suspicion
Carbon monoxide poisoning is easy to miss because its early symptoms overlap with the flu: headache, nausea, weakness, and dizziness. The critical difference is that CO poisoning does not cause a fever, and symptoms tend to improve when you leave the building and worsen when you return. If more than one household member develops these symptoms around the same time, CO should be high on your list of suspects.
As exposure continues, symptoms escalate in a predictable pattern. Mild exposure causes headaches and irritability. Moderate exposure adds drowsiness, difficulty thinking, blurred vision, and severe headaches. Severe exposure leads to a racing heart, loss of muscle control, confusion, seizures, and loss of consciousness. The progression can happen over hours with a slow leak or within minutes at high concentrations.
Pay special attention to these clues during heating season: symptoms that come and go with time spent at home, multiple family members or pets feeling unwell simultaneously, and headaches that ease after spending time outdoors.
What Happens at the Hospital
Emergency responders and hospital staff will give you high-concentration oxygen, typically through a mask. Carbon monoxide works by binding to your red blood cells in place of oxygen, essentially starving your organs. Breathing concentrated oxygen forces the CO molecules off your blood cells and restores normal oxygen delivery.
A blood test measuring the percentage of your hemoglobin bound to CO confirms the diagnosis. Standard fingertip pulse oximeters are unreliable here because they cannot distinguish between oxygen-carrying and CO-carrying hemoglobin, which is why a direct blood draw is necessary. Levels above 25% are considered severe poisoning.
In certain cases, treatment involves breathing pure oxygen in a pressurized chamber. This is typically recommended when someone lost consciousness, shows neurological changes like confusion or coordination problems, has heart-related complications, or is pregnant with CO levels above 20%. The pressurized environment forces CO off hemoglobin far more efficiently than a regular oxygen mask.
Why Pregnant Women and Children Face Higher Risk
Pregnant women need to take any potential CO exposure especially seriously. Fetal hemoglobin binds carbon monoxide even more tightly than adult hemoglobin, meaning the concentration of CO in fetal blood can run about 15% higher than in the mother’s blood. Even after the mother’s levels return to normal with oxygen therapy, the fetus may still carry dangerous levels. Research shows a pregnant woman may need oxygen therapy five times longer than it takes for her own blood to clear in order to protect the baby.
Young children, older adults, and people with heart or lung conditions are also at greater risk. Children breathe faster and have smaller bodies, so they absorb CO more quickly. People with existing heart disease can develop dangerous cardiac complications at lower exposure levels than healthy adults.
Common Household Sources
Carbon monoxide comes from anything that burns fuel. The most frequent culprits inside homes are gas furnaces, water heaters, gas stoves and ovens, fireplaces, wood stoves, and attached garages where cars idle. Portable generators and charcoal grills used indoors or in enclosed spaces are responsible for a large share of fatal poisonings, particularly during power outages.
Blocked chimney flues, cracked heat exchangers in furnaces, and backdrafting from poor ventilation are the structural failures that most often cause CO to accumulate. A furnace can operate for years with a small crack that slowly worsens, which is why annual professional inspections of all fuel-burning appliances matter.
After the Immediate Emergency
Once emergency responders clear your home, a technician should identify and repair the CO source before you use any fuel-burning appliances again. Your fire department or gas utility company can often help locate the problem during their initial response.
Even after treatment, watch for delayed neurological symptoms. Up to 40% of people with significant CO exposure develop what’s called a delayed neuropsychiatric syndrome, which can appear anywhere from 3 days to 8 months after the initial poisoning. Symptoms include memory problems, difficulty concentrating, personality changes, depression, anxiety, and movement difficulties. These can be alarming, but 50 to 75% of people recover within a year. If you notice cognitive or mood changes in the weeks following exposure, bring them to your doctor’s attention and mention your CO exposure history.
Preventing It From Happening Again
Install a carbon monoxide detector on every floor of your home. If you can only afford one, place it near the bedrooms and make sure the alarm is loud enough to wake you. Battery-operated units should be tested weekly, with fresh batteries at least once a year. Detectors have a limited sensor lifespan, so check the manufacturer’s replacement date printed on the unit and swap it out on schedule.
Have a qualified technician inspect your furnace, water heater, and any other gas or oil-burning appliances once a year, ideally before heating season. Never run a generator, grill, or camp stove inside your home, garage, or any enclosed area. Never use your gas oven or stovetop burners to heat your home. Keep vents and chimneys clear of debris, snow, and animal nests. These steps are straightforward, but they account for the vast majority of preventable CO deaths each year.