us Health & medical scares

What to do if…
a carbon monoxide alarm sounds and you feel sick or have a headache

Produced and maintained by PanicStation.org Published: 30 May 2026 Last reviewed: 17 July 2026 Editorial policy USA guide

Short answer

Stay outside in fresh air, keep everyone out, and call 911 now. Tell the dispatcher that a carbon monoxide alarm sounded and that someone has headache or nausea. Do not go back inside until emergency responders say it is safe.

Do not do these things

Do not re-enter to silence, reset, or check the alarm.
Do not go back inside to look for the source or operate, turn off, or check equipment.
Do not assume it is a false alarm because you cannot smell anything. Carbon monoxide has no smell.
Do not delay calling 911 while contacting a landlord, utility company, or Poison Help.
Do not use a generator indoors or in a garage. Keep generators outdoors more than 20 feet from windows, doors, and vents.
Do not use a grill or camp stove indoors or near building openings.
Do not run a vehicle in an attached garage, even with the garage door open.
Do not drive yourself if you feel dizzy, confused, unusually sleepy, faint, or very unwell.

What to do now

Stay outside and keep everyone out. Move to a safe spot away from the building, its open windows and doors, garages, generators, and idling vehicles.
Call 911 now. Say that a carbon monoxide alarm sounded and that someone has headache or nausea. Give the address and follow the dispatcher’s instructions.
Account for everyone who was inside. Tell the dispatcher immediately if any person or pet may still be inside. Do not re-enter.
Report urgent symptoms clearly. Tell the dispatcher if anyone has trouble breathing, chest pain, fainting, seizure, confusion, worsening symptoms, or difficulty staying awake.
Mention factors that may matter to responders or clinicians. Say if anyone exposed is pregnant, a baby or infant, an older adult, or has chronic heart disease, anemia, or a respiratory illness.
Use Poison Help as an additional expert route without delaying 911. Another adult can call 1-800-222-1222 while the 911 call is underway. Otherwise, call Poison Help after speaking with 911 if you need additional poison-exposure guidance.
Wait for responder permission before re-entering. If responders identify a malfunctioning appliance, do not use it again until trained personnel have serviced it.
Give responders or clinicians the key details. Include when the alarm sounded, when you left, who was inside, symptoms, and possible sources such as a furnace, water heater, stove, fireplace, generator, or vehicle near a garage.

What can wait

Troubleshooting the detector or deciding whether it needs replacement.
Finding the exact source yourself.
Calling a landlord, homeowners association, insurer, or gas utility unless responders tell you to do so now.
Retrieving belongings.
Arranging repairs before responders have said the space is safe to enter.

Important reassurance

Getting outside was the right first step. Headache or nausea after a carbon monoxide alarm is a valid reason to treat the alarm seriously and call for help.

Scope note

These are first steps only. Medical assessment, repairs, inspection, and later prevention decisions may need help from emergency responders, clinicians, or qualified technicians.

Important note

This is general information, not medical or other professional advice. Call 911 now for a sounding carbon monoxide alarm with headache or nausea, and do not re-enter until emergency responders say it is safe.

Additional Resources

About this guide

This guide was produced and is maintained by PanicStation.org using its published editorial process. Official and specialist sources are checked where relevant, and AI-assisted tools may be used for drafting, organisation, and consistency checks. The site operator remains responsible for publication, revision, and removal decisions.

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