CO Symptoms Action Check

WARNING: If you are currently experiencing severe symptoms - confusion, difficulty walking, chest pain, loss of consciousness - or if your CO alarm is sounding, leave the building immediately and call 911. Do not continue with this action check first.

Carbon monoxide symptoms often overlap with the flu, food poisoning, altitude sickness, and migraine. Headache, nausea, dizziness, and fatigue are common to all of them. The key difference is context: Do symptoms improve when you leave the building? Are multiple people or pets affected at the same time?

This 1-minute action check asks five questions about symptoms, exposure context, and who else is affected. It helps you decide whether to leave now, call 911, call Poison Control, or keep monitoring while you investigate the source.

There is a group of readers for whom symptoms are not the second signal but the first, and the law has noticed. A carbon monoxide alarm announces itself by sound, so an occupant who is deaf or hard of hearing may never be told anything until the symptoms start. Six of the 51 US jurisdictions we track write an accommodation into their carbon monoxide rules rather than leaving it to general accessibility law, and they form a ladder. Iowa and Ocean City, Maryland require a suitable detector to be made available on request. Stamford, Connecticut and Cleveland, Ohio require one on request, and Cleveland alone names it as visual or vibrating. New Jersey goes furthest of the standing duties: at a tenant's request the owner must provide and install a visual-alarm detector in a multiple dwelling where a deaf or hearing-impaired person lives. Maine is the only one that says what happens when the owner refuses - under 25 M.R.S. 2468(3) the occupant may buy the detector, install it, maintain it and deduct the cost from the rent, protected by name from retaliation, eviction or penalty for doing so.

This is not a diagnosis tool. It is a safety action tool. When in doubt, leave the building and call 911. Carbon monoxide exposure can escalate quickly.

In 60 Seconds

• CO symptoms often mimic the flu: headache, nausea, dizziness, fatigue, and confusion.
• The strongest clue is context: symptoms improve outside, multiple people feel sick, and pets may also act unwell.
• Children, older adults, pregnant individuals, and people with heart or lung conditions can be affected faster and at lower concentrations.
• Even mild symptoms deserve prompt safety action and medical follow-up when appropriate.
• When in doubt, get out. Leave the building, call 911 from outside, and do not re-enter until responders clear it.

What This Check Covers

• What symptoms are happening right now and whether any are severe.
• Whether symptoms improve when you leave the building.
• Whether multiple people or pets in the same location are affected.
• Whether a likely CO source is nearby.
• Whether anyone affected is in a vulnerable group.

Start the Check

How to Interpret Your Result

This action check routes symptom-and-exposure patterns to the safest next step using CDC, CPSC, Poison Control, and clinical reference guidance.

• Monitor Symptoms and Check the Environment:Your answers do not strongly match the classic CO exposure pattern. Monitor your symptoms, verify that CO detectors are working, and call Poison Control or your doctor if symptoms persist.
• Leave and Get Guidance Now:Your symptoms and context are consistent with possible carbon monoxide exposure. Leave the building, call Poison Control, and do not re-enter until the building has been checked.
• Leave Now and Call 911:Your symptoms and context strongly suggest a dangerous exposure pattern. Leave immediately, call 911 from outside, and go to the nearest emergency room.

Sources & References

1. Maine Legislature, 25 M.R.S. 2468(3), carbon monoxide detectors, accommodation and rent-deduction remedy. The only accommodation in the fifty-one that says what happens when the owner refuses. An occupant who is deaf or hard of hearing may ask for a suitable detector; where the owner does not supply one, the occupant may buy, install and maintain it, deduct the cost from the rent, and is protected by name from retaliation, eviction or penalty.
2. New Jersey Administrative Code, N.J.A.C. 5:10-28.1(c), visual-alarm carbon monoxide detector on request. The strongest standing duty of the six: at a tenant's request, the owner of a multiple dwelling in which a deaf or hearing-impaired person resides must provide and install a visual-alarm type detector. Every other accommodation in the set stops at making a device available.
3. Iowa Legislature, Iowa Code 10A.518(3)(c), carbon monoxide alarm accommodation. The owner of a covered multiple-unit residential building, or the owner's agent, must supply an alarm suitable for a guest who is deaf or hard of hearing. Written into the carbon monoxide statute rather than left to general accessibility law.
4. CDC, CO Poisoning Basics. More than 400 deaths a year, more than 100,000 emergency department visits and more than 14,000 hospitalizations; symptoms and prevention.
5. CDC, Clinical Guidance for CO Poisoning. Treatment protocols, COHb interpretation.
6. CPSC, CO Questions and Answers. PPM symptom thresholds, alarm standards.
7. Mayo Clinic, Carbon Monoxide Poisoning. Symptoms, when to see a doctor, causes, prevention.
8. Cleveland Clinic, Carbon Monoxide Poisoning. Severity staging and emergency warning signs.
9. StatPearls/NCBI, Carbon Monoxide Toxicity. Symptom percentages, COHb thresholds, delayed neurological sequelae.
10. Johns Hopkins Medicine, Carbon Monoxide Poisoning. Names the look-alikes in the source's own words, flu and food poisoning, with the symptom list and when to get help.
11. OSHA Susan Harwood grant handout, Effects of Carbon Monoxide at Different Concentrations. Concentration, exposure time and effect from 35 ppm to 12,800 ppm. Produced under grant SH-27664 and carries the grainsafety.org footer, so only the 50 ppm eight-hour permissible exposure limit in it is OSHA's own rule.
12. AAP, Carbon Monoxide Exposure. Pediatric-specific susceptibility.
13. Poison Control, Carbon Monoxide Poisoning. Emergency guidance, 1-800-222-1222.