- HVAC
- Smoke and CO alarms
ARO-ROJO-CO
Nest Protect red ring on CO alarm: carbon monoxide emergency
Risk level
Critical
Stop using the equipment and contact a professional.
Urgency
Immediate
Quick answer
Get everyone into fresh air, call 112 or your local emergency number and stay out until emergency services tell you otherwise: a red ring, the siren and 'Emergency. There's carbon monoxide in the...' mean CO at emergency level.
Safety first
What to do now
- Move everyone to fresh air and call 112
Who: you and everyone in the home, without staying to find where the gas comes from. How: go straight outdoors or to an open door or window, open doors or windows only if they are on your way out, count everyone and call 112 or your local emergency number; tell the operator if anyone feels unwell. Result that matters: getting everyone away from the CO before doing anything else. If everyone is in fresh air: stay there and wait for emergency services. If someone is still inside or has symptoms: tell the emergency operator right away and do not go back in yourself. Evidence to keep: the time of the alarm, the room announced and anyone with symptoms.
- Wait until the home is aired and the alarm is normal
Who: you, outside or beside the open door or window. How: Google says not to re-enter or move away from fresh air until emergency responders arrive, the home has been aired out and the alarm returns to its normal condition. Result that matters: not exposing yourself again to a gas you cannot see or smell. If responders clear you to go in: listen for the Protect saying the carbon monoxide alarm is over. If the alarm continues or you are asked to wait: stay outside and follow their instructions. Evidence to keep: who cleared you to go back in and at what time.
- If it sounds again within 24 hours, call a technician
Who: you and a qualified gas or fuel-burning appliance technician. How: if the alarm reactivates within 24 hours, repeat the steps of leaving and calling emergency services, then have a technician inspect all combustion equipment; do not use it until it has been checked. Result that matters: finding the appliance producing CO rather than just silencing the alarm. If the technician finds a problem: Google says the equipment must be serviced immediately. If some appliance was not inspected: check its manufacturer's instructions on CO safety. Evidence to keep: a dated list of appliances inspected and not inspected.
- Check the garage once it is safe to go in
Who: you, only after emergency services give the all-clear. How: make sure no car or motorbike has been left running in an attached garage or next to the house, as Google's guidance asks. Result that matters: ruling out a CO source that has nothing to do with household appliances. If an engine was running: tell emergency services and the technician. If no vehicle was running: the appliance inspection becomes the priority. Evidence to keep: a note on vehicles and garage use in the hours before the alarm.
What you must never do
- Do not attempt this professional task: Emergency services for carbon monoxide
- Do not attempt this professional task: Gas technician inspection of combustion appliances
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Emergency services for carbon monoxide
What they doCalling 112 or your local emergency number sends responders who air out the home and decide when it is safe to go back in.
They must show youthe CO reading they measured, if they took one, and in which room.
In writingthe time of the call-out and the all-clear to go back in.
Gas technician inspection of combustion appliances
What they doA qualified technician inspects boilers, water heaters, stoves and other fuel-burning equipment to find the CO source.
They must show youthe flue gas analysis of each appliance inspected.
In writingwhich appliance was the source, the repairs carried out and which equipment was not inspected.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- HVAC
- Brand
- Google Nest
- Product type
- Smoke and CO alarms
Known code variants
- Emergencia. Hay monóxido de carbono en
- Emergency. There's carbon monoxide in the
- Google Nest Protect alarma de monóxido de carbono
- Google Nest Protect carbon monoxide emergency
- Nest Protect alarma CO suena
- Nest Protect aro rojo monóxido
- Nest Protect CO alarm going off
- Nest Protect Emergencia hay monóxido de carbono
- Nest Protect move to fresh air
- Nest Protect red ring carbon monoxide
- Nest Protect sal al aire libre
What it means
With this alarm, get everyone to fresh air, call 112 or your local emergency number and do not go back in until emergency services say so. Google's 'Nest Protect lights and sounds' page says the red ring with the siren and 'Emergency. There's carbon monoxide in the (room name). Move to fresh air' means CO in that room has reached emergency levels. CO is invisible and odourless. If the alarm comes back within 24 hours, Google asks for a qualified technician to inspect fuel-burning appliances. These details apply to the 2nd gen Nest Protect, and other models may behave differently. The light or sound alone never proves a fault: treat it as a real emergency.
Warnings and stop conditions
- Highsource verified
Pressing the centre button only silences the alarm temporarily and it sounds again if the problem continues: it is no substitute for getting to fresh air and calling emergency services.
Evidence: Nest Protect lights and sounds · What to do if carbon monoxide is detected
- Highsource verified
Carbon monoxide can be fatal and you cannot see or smell it: even if nothing seems wrong, treat the red ring as an emergency.
Evidence: What to do if carbon monoxide is detected
Sources and technical references
- 1
Nest Protect lights and sounds
Google · 2026 · official_doc
- 2
Luces y sonidos de Nest Protect
Google · 2026 · official_doc
- 3
What to do if carbon monoxide is detected
Google · 2026 · official_doc
- 4
Qué hacer si se detecta monóxido de carbono
Google · 2026 · official_doc
- 5
The difference between Protect's Heads-Up and Emergency Alarms
Google · 2026 · official_doc
- 6
Diferencias entre las funciones Aviso y Alarma de emergencia de Protect
Google · 2026 · official_doc
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