Carbon monoxide is often called the “silent killer,” because the invisible and odorless gas can be deadly. Even just a few minutes of breathing in fumes that contain carbon monoxide (CO) can cause life-threatening illness.

In March, 14-year-old Miller Gardner, the son of former New York Yankees player Brett Gardner, died from carbon monoxide poisoning while vacationing with his family at a beach resort in Costa Rica.

Just a month earlier, three American women were found dead in their hotel room in Belize, also due to carbon monoxide exposure, likely caused by a faulty instant water heater.

While many U.S. homes are equipped with carbon monoxide monitors, travelers may be at greater risk. Recognizing causes and symptoms of carbon monoxide poisoning and taking prevention measures can help avoid tragedy.

Signs and Symptoms of Carbon Monoxide Poisoning

Early symptoms of carbon monoxide exposure include:

Nausea
Mild headache
Shortness of breath

Symptoms of moderate exposure and more advanced symptoms include:

Chest pain
Dizziness and weakness
Mental confusion
Loss of muscle coordination
Fainting (loss of consciousness)
Severe headache
Upset stomach, including nausea and vomiting

Low levels of carbon monoxide may cause delayed symptoms. Those fumes are still toxic and can harm your health the longer you breathe them in. If you suspect you’ve been exposed to carbon monoxide, get out of the exposure area immediately, breathe fresh air, and seek emergency care.

Causes and Risk Factors of Carbon Monoxide Poisoning

Many fuel-burning engines and appliances expel carbon monoxide. In areas with inadequate airflow or venting, the amount of carbon monoxide in the air may rise to dangerous levels. For example, using a charcoal grill indoors or leaving a running car inside a garage puts people at risk.

When too much carbon monoxide is in the air and people breathe it in, the gas replaces oxygen in their blood cells. The buildup of carbon monoxide in the blood can lead to serious tissue damage, loss of consciousness, and suffocation within minutes.

In the winter, risks are higher when people use fuel-burning heating systems. However, the summer months can also be risky.

“That’s often the time that people do more home improvement projects, and sometimes use gas-powered tools such as power washers inside their homes,” says Jeffrey S. Cooper, MD, a professor of emergency medicine at the University of Nebraska College of Medicine in Omaha.

Who Is at Highest Risk of Carbon Monoxide Poisoning?

People at the highest risk of carbon monoxide poisoning at low doses of exposure include:

Developing fetuses
Infants
People over age 65
People living at high altitudes
People with chronic heart disease, anemia, or respiratory conditions
Smokers

People who are a smaller size and pets may see carbon monoxide effects sooner — pets are usually the first in a household to show symptoms.

Anyone who works around combustion engines or fires is at a higher risk for carbon monoxide poisoning. Higher CO levels are likely in places such as boiler rooms, warehouses, and petroleum refineries.

Careers linked with a higher risk of carbon monoxide poisoning include:

Firefighters
Mechanics
Drivers
Welders

Carbon Monoxide Poisoning, Natural Disasters, and Power Outages

Portable generators come in handy when natural disasters cause a power outage because they can help keep homes warm or run appliances. However, power generators produce carbon monoxide and can be dangerous if not used properly.

Treatments for Carbon Monoxide Poisoning

People with carbon monoxide poisoning are given 100 percent oxygen through a mask until they feel better, which is usually within four to five hours.

During this time, healthcare staff will perform regular neurologic exams to track progress and watch for signs of brain swelling.

People with especially high carbon monoxide levels in the blood may be given hyperbaric oxygen therapy, which is the delivery of pure oxygen in an enclosed space with higher than normal air pressure.

Hyperbaric oxygen therapy is the preferred treatment for pregnant women, even if their poisoning isn’t severe.

Prevention of Carbon Monoxide Poisoning

Carbon monoxide is produced by any home appliance that uses natural gas and burns fuel in your home, such as a furnace, stove, clothing dryer, or gas-powered generator. All fuel-burning appliances need to be vented outside.

Gas-powered car engines release carbon monoxide as well, so never leave a car running in an enclosed garage connected to the home.

Other prevention tips include:

Use carbon monoxide detectors and check them regularly. Place them near each sleeping area on every level of the house and check the batteries at least twice a year.

If the alarm sounds, don’t immediately blame a faulty battery. Remember, the gas is invisible and odorless, and you should trust the detector. Leave the house and call 911 or emergency medical help. Carbon monoxide detectors also are made for motorhomes and boats.

Utilize gas appliances only as intended. Don’t use a gas stove or oven for heat and don’t use gas camp stoves indoors. Don't run a generator in an enclosed space, such as a basement, garage, or tent, even if the garage door or windows are open.

When your garage door is open, you’re pulling air in, not exhausting it out, says Dr. Cooper.

“We've seen patients come to the ER badly poisoned saying, ‘I had the garage door open. Why did this happen?’ Opening a door or window isn’t enough — generators and gas-powered devices should really be outside,” he says.

Have appliances checked regularly. Have professionals set up all gas-, oil- or coal-burning appliances, and have a qualified service professional check them yearly.

Keep fireplaces in good condition. Clean the fireplace chimney and flue every year.

Do repairs before returning to a place where poisoning occurred. If carbon monoxide poisoning happens in your home, have a professional find and repair the source before staying there again.

How to Avoid Carbon Monoxide Poisoning While Traveling

Cooper offers a few tips to stay safe while traveling:

Check the listing on your rental or call ahead to your hotel or resort and ask if they have carbon monoxide detectors. “Most, but not all states require hotels to have CO detectors,” he says.
Buy a portable carbon monoxide detector and take it with you on trips. Small devices can be purchased online for between $20 and $35.

The detector should beep a few times when you plug it in to let you know it’s working. (Follow the instructions that came with the device.) If the alarm beeps during your stay, leave the house or building immediately.

Common Questions & Answers

What should I do if I suspect carbon monoxide poisoning?

Immediately leave the area and call emergency services. Don’t ignore a carbon monoxide detector’s alarm or symptoms, even if they seem mild.

How can I protect myself from carbon monoxide poisoning while traveling?

Ask hotels or rental properties if they have carbon monoxide detectors and consider bringing a portable one. Always leave a building immediately if the detector goes off.

What are the symptoms of carbon monoxide poisoning?

Common symptoms include nausea, headache, dizziness, chest pain, confusion, and fainting. Severe cases can lead to loss of consciousness or even death.

Can carbon monoxide poisoning be treated?

Yes, treatment typically involves 100 percent oxygen delivered through a mask or hyperbaric oxygen therapy in severe cases.

Is it safe to use a portable generator during a power outage?

Portable generators should only be used outdoors. Never use them inside enclosed spaces like homes, trailers, tents, or garages.

Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.

Resources

Carbon Monoxide Poisoning. Mayo Clinic. March 28, 2025.
Mather V. Ex-Yankees Player Brett Gardner’s Son Died From Carbon Monoxide, Officials Say. The New York Times. April 3, 2025.
Romero D et al. 3 Americans in Belize Died from Carbon Monoxide in Hotel Room, Officials Say. NBC News. March 28, 2025.
Carbon Monoxide Poisoning Basics. Centers for Disease Control and Prevention. April 17, 2024.
Carbon Monoxide Poisoning. Cleveland Clinic. July 20, 2023.
Generators and Engine-Driven Tools. United States Consumer Product Safety Commission.
Clinical Guidance for Carbon Monoxide Poisoning Following Disasters and Severe Weather. Centers for Disease Control and Prevention. July 8, 2024.

Michael S. Niederman, MD

Medical Reviewer

From NewYork-Presbyterian, Castle Connolly Top Doctor

Michael S. Niederman, MD, is the lead academic and patient quality officer in the division of pulmonary and critical care medicine at Weill Cornell Medical Center in New York City; a professor of clinical medicine at Weill Cornell Medical College; and Lauder Family Professor in Pulmonary and Critical Care Medicine. He was previously the clinical director and associate chief in the division of pulmonary and critical care medicine at Weill Cornell Medical Center.

His focus is on respiratory infections, especially in critically ill patients, with a particular interest in disease pathogenisis, therapy, and ways to improve patient outcomes. His work related to respiratory tract infections includes mechanisms of airway colonization, the management of community- and hospital-acquired pneumonia, the role of guidelines for pneumonia, and the impact of antibiotic resistance on the management and outcomes of respiratory tract infections.

He obtained his medical degree from Boston University School of Medicine, then completed his training in internal medicine at Northwestern University School of Medicine, before undertaking a pulmonary and critical care fellowship at Yale University School of Medicine. Prior to joining Weill Cornell Medicine, he was a professor in the department of medicine at the State University of New York in Stony Brook and the chair of the department of medicine at Winthrop-University Hospital in Mineola, New York, for 16 years.

Dr. Niederman served as co-chair of the committees that created the American Thoracic Society's 1993 and 2001 guidelines for the treatment of community-acquired pneumonia and the 1996 and 2005 committees that wrote guidelines for the treatment of nosocomial pneumonia. He was a member of the American Thoracic Society/Infectious Diseases Society of America committee that published guidelines for community-acquired pneumonia in 2007. He was also the co-lead author of the 2017 guidelines on nosocomial pneumonia, written on behalf of the European Respiratory Society and the European Society of Intensive Care Medicine.

He has published over 400 peer-reviewed or review articles, and has lectured widely, both nationally and internationally. He was editor-in-chief of Clinical Pulmonary Medicine, is an associate editor of Critical Care and the European Respiratory Review, and serves on the editorial boards of Critical Care Medicine and Intensive Care Medicine. He has previously served on the editorial boards of the American Journal of Respiratory and Critical Care Medicine and Chest. For six years, he was a member of the Board of Regents of the American College of Chest Physicians, and in 2013, he was elected as a master of the American College of Physicians.

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Becky Upham

Author

Becky Upham has worked throughout the health and wellness world for over 25 years. She's been a race director, a team recruiter for the Leukemia and Lymphoma Society, a salesperson for a major pharmaceutical company, a blogger for Moogfest, a communications manager for Mission Health, a fitness instructor, and a health coach.

Upham majored in English at the University of North Carolina and has a master's in English writing from Hollins University.

Upham enjoys teaching cycling classes, running, reading fiction, and making playlists.

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COPD

What Is Carbon Monoxide Poisoning?

Overview