Carbon Monoxide Alarm Going Off in Apartment: What Renters Should Do

A carbon monoxide alarm can feel confusing because CO is invisible and odorless. You may not see smoke, flames, or obvious appliance problems. That is exactly why the alarm matters. It is designed to warn you before you can detect the danger yourself.

This guide is general safety information for renters. It is not medical advice, legal advice, or a code inspection. If an alarm sounds or you suspect CO exposure, prioritize leaving and calling emergency services.

What to do immediately

1. Leave the apartment right away.
2. Get everyone to fresh air, including children, guests, roommates, and pets if safe.
3. Call emergency services or your local emergency number from outside.
4. Do not go back inside to find the source.
5. Do not silence, unplug, or remove the alarm until the situation is checked.
6. Wait for responders or qualified professionals to say it is safe to re-enter.

Do not assume it is a false alarm

CO alarms can sound for different reasons, including real carbon monoxide, end-of-life warnings, battery issues, or device malfunction. Renters should not guess during an active alarm. Leave first and let responders or qualified professionals determine what happened.

If the alarm later appears to be malfunctioning, that still needs follow-up. A broken or expired alarm should be reported and replaced.

Possible symptoms of carbon monoxide exposure

CO exposure may cause symptoms such as headache, dizziness, weakness, nausea, vomiting, confusion, chest discomfort, or flu-like feelings. Symptoms can vary, and some people may be affected faster than others.

If anyone feels unwell, tell emergency responders. Do not drive yourself if you feel dizzy, confused, weak, or unsafe.

Common CO sources in apartments

• Gas furnaces, boilers, or water heaters
• Gas stoves or ovens used improperly
• Fireplaces or blocked vents
• Attached garages or vehicle exhaust
• Shared mechanical rooms
• Portable generators used too close to the building
• Charcoal grills, camp stoves, or outdoor cooking devices used indoors

For prevention basics, read Carbon Monoxide Safety for Renters.

What renters should not do

• Do not ignore the alarm because you feel fine.
• Do not remove batteries to stop the sound.
• Do not open windows and remain inside as your only response.
• Do not search for the source before leaving.
• Do not restart fuel-burning appliances yourself.
• Do not re-enter until responders or qualified professionals say it is safe.

After the emergency response

After the immediate danger is handled, ask what was found and what needs repair. If the issue involves a building appliance, shared system, or landlord-owned equipment, contact your landlord or property manager in writing.

Keep the message factual. Include the alarm location, time, responder instructions, and any repair recommendations you were given.

How to document the incident

1. Write down the date and time the alarm sounded.
2. Note which alarm sounded and where it is located.
3. Save any incident number or responder notes if provided.
4. Take photos of alarms or appliance areas only when it is safe.
5. Send a written follow-up to the landlord.
6. Keep repair orders and replacement confirmations.

The Renter Safety Documents Checklist can help you keep these records organized.

If your apartment has no CO alarm

If you discover that your apartment has no carbon monoxide alarm, or the alarm is missing, expired, damaged, or not working, report it. Requirements vary by location, but a missing alarm is still a serious safety concern.

Read What To Do If Your Apartment Has No Carbon Monoxide Alarm and use the Carbon Monoxide Alarm Placement Checker.

Bottom line

A carbon monoxide alarm is not a nuisance alarm to debate from inside the apartment. Leave, get fresh air, call emergency services, and wait for clearance before returning. Afterward, document the incident and make sure the cause and alarm status are addressed.