Carbon monoxide detectors going off can be unsettling. It may be hard to know what to do first. There are simple, sensible steps you can take right away.

Why This Situation Matters

A detector alarm may mean there are elevated levels of an unseen gas in your home. That can cause headaches, nausea, or feeling lightheaded for some people. Even if it turns out to be a false alarm, the sound usually means something needs checking. Ignoring it can cause disruption and make it harder to know what went wrong later.

What to Do Immediately

1. Stay calm and note the alarm — Listen to the pattern and timing of the sound and try to remember when it started.
2. Check how people feel — Ask everyone if they have headaches, nausea, dizziness, or trouble concentrating. If someone feels unwell, move them to fresh air and consider seeking medical advice.
3. Open windows and doors — Let fresh air into the area to reduce any buildup.
4. Turn off fuel-burning appliances if easy to do — If it is simple and safe, switch off stoves, fireplaces, or other fuel appliances and avoid using them.
5. Step outside or go to a well-ventilated area — Spend time in fresh air away from the building while you assess the situation.

Things to Avoid

• Do not ignore the alarm — Assuming it is a false alarm can delay finding the cause.
• Do not disable or remove the detector — Turning it off without addressing the reason may hide a real problem.
• Do not use open flames or run gas appliances — This can add fuel to a problem if one exists.
• Do not climb into or tamper with vents or the appliance itself — Avoid actions that need tools or skills.

What to Do Next

Watch the detector and note any changes. Check the unit’s display or indicator lights if that is easy to do. Document the time the alarm sounded and any symptoms or events, like running a car in a closed garage earlier. If you rent, tell your landlord or building manager. You can also consult the detector’s manual or the manufacturer’s support line for non-technical guidance. Avoid using fuel-burning appliances until the situation is looked at.

When to Get Professional Help

Professional help may be appropriate if the alarm keeps sounding, if symptoms continue, or if you are unsure about the cause. You might contact a licensed HVAC or gas technician, your gas utility, the detector’s manufacturer, building management, or a healthcare provider depending on the concern. Professionals can check appliances, ventilation, and the detector itself in a safe way.

Quick Summary

• Note the alarm pattern and how people feel.
• Open windows, turn off simple fuel appliances if safe, and get fresh air.
• Do not disable the detector or use open flames.
• Seek professional help if the alarm persists or anyone remains unwell.

About the Author

Situation Guide Editorial Team

The Situation Guide editorial team writes clear, practical guides for common real-world situations. Content focuses on safe first steps, plain-language explanations, and helping readers recognise when professional help may be appropriate. This guide provides general information only and is not a substitute for personalised professional advice. Specific circumstances can vary.