Short answer: Yes. If a carbon monoxide (CO) alarm sounds, get everyone outside to fresh air even if there is no smell and nobody feels ill. Call emergency services from outside: 119 in South Korea, or the local emergency number elsewhere. Do not stay inside to find the source, open windows as a substitute for leaving, or reset the alarm and wait. A quiet alarm is not permission to go back in; wait for emergency responders to clear re-entry.
Why no smell is not reassuring
CO has no color or odor. Fuel-burning heating equipment, generators, charcoal and vehicle exhaust can produce it. Natural gas appliances are not exempt. You cannot check for CO by sniffing the air.
This guidance applies to a CO hazard alarm or suspected exposure in a home, rental accommodation or camping setting. A smoke alarm is not automatically a CO alarm. Learn your actual device’s functions and warning signals from its manual before an incident; do not assume an unfamiliar alarm is a harmless battery warning while remaining in the building.
Leave first, report second, return only when cleared
- Get outside: Wake other occupants and move to fresh air. Do not delay to locate the appliance or collect belongings.
- Call from safety: Give emergency services the address, the CO alarm report, the number of people out or still inside, and any symptoms. Do not re-enter to attempt a rescue; tell responders where the person may be.
- Wait for clearance: Do not return until responders permit it. Any appliance identified as the source needs professional servicing before reuse.
US CPSC and Health Canada guidance both prioritize leaving and calling from outside. Opening a window does not make a hazardous building safe to occupy. Fuel-powered generators must not run in a garage, even with its doors or windows open.
What if the alarm is silent or symptoms seem mild?
Similar headaches, dizziness or nausea in several people around fuel-burning equipment is an exposure clue worth reporting, not a diagnosis. Do not simply label it flu or tiredness and stay in the same space. Suspected exposure calls for fresh air and immediate medical help.
Confusion, reduced consciousness, fainting, seizures, chest pain or breathing difficulty needs emergency assistance. Tell responders about infants, pregnancy, older age, heart or lung disease, or anemia. Feeling better after leaving does not prove that exposure was harmless.
A normal fingertip oxygen reading cannot rule it out
A standard pulse oximeter can be inaccurate when carboxyhemoglobin (COHb) is present. A reassuring-looking oxygen saturation number is therefore not a CO clearance test. Clinicians assess the exposure history and symptoms, and may measure blood COHb. Do not delay evacuation or a call to repeat home readings.
After medical assessment, follow the discharge and follow-up instructions. New problems with memory, concentration or walking after an apparent recovery may require reassessment.
Use local emergency and product guidance
South Korea’s National Fire Agency camping guidance, published September 4, 2026, addresses combustion-heater hazards in enclosed spaces, CO alarms and emergency calls to 119. US and Canadian pages use 911. Use the emergency number where you are, and follow local certification rules and the actual alarm manufacturer’s installation, testing and replacement instructions. Do not transfer one country’s alarm patterns or placement advice to every product.
What to record and ask once safely outside
If available, note when the alarm and symptoms began, when you left, who was present, the equipment and fuel in use, pregnancy and relevant medical conditions. Never go back for photos or postpone the emergency call to complete a record.
- Does the exposure history call for medical assessment or a COHb test?
- Which delayed symptoms or changes mean I should return for care?
- Who must check the premises and appliance before re-entry or reuse?
Related reading
- Symptom timeline and visit questions — for organizing information after leaving and calling
- Home pulse oximeter readings and when to seek care — suspected CO exposure cannot be cleared by a normal reading
Sources and review date
- US CPSC: Carbon Monoxide Questions and Answers — alarm response, re-entry and appliance servicing.
- Health Canada: Carbon monoxide — Preventing exposure.
- CDC: Carbon Monoxide Poisoning Basics (January 12, 2026).
- CDC: Clinical Guidance for Carbon Monoxide Poisoning (reviewed August 21, 2026).
- NIH/NLM MedlinePlus: Carbon monoxide poisoning (reviewed January 8, 2025).
- South Korea National Fire Agency: Camping safety guidance (September 4, 2026; Korean).
Reviewed October 17, 2026. General health and safety information based on official public sources; not a personal poisoning diagnosis, treatment plan or substitute for on-scene emergency instructions.