Carbon monoxide warning and immediate action

Core idea

Carbon monoxide is produced by incomplete combustion and cannot be seen or smelled. Headache, dizziness, nausea, weakness, confusion, chest pain or breathlessness can be warning signs, especially when several people are affected or symptoms improve outside. A carbon monoxide alarm provides warning; it does not prevent production or prove an appliance is safe.

What to recognise

• Treat a sounding alarm or suspected exposure as real and get everyone into fresh air.
• Seek prompt medical advice for possible symptoms; severe symptoms require 999.
• Stop using suspect appliances and report the gas emergency from a safe place.
• Do not re-enter or restore use until appropriate advice and competent checks allow it.
• Install and maintain alarms in the locations and manner required by current guidance and the manufacturer.

Apply it

When a customer reports repeated headaches with a lazy yellow flame or staining, protect people before discussing servicing. Do not delay departure to investigate, open every window or reach an unsafe control. Once safe, the emergency route and a Gas Safe registered investigation deal with the source.

When Approved Document J calls for an alarm

In England, where a new or replacement fixed gas appliance is installed in a dwelling, Approved Document J says a carbon monoxide alarm should be provided in the room where the appliance is. Appliances used solely for cooking are excluded, and extending pipework installs no appliance. The alarm should meet BS EN 50291-1 and run on a battery designed to last its working life, with a warning when that life is ending. A fixed-wired mains Type A alarm with a sensor-failure warning is the alternative; a plug-in alarm is not. It goes on the ceiling at least 300 mm from any wall, or high on a wall above any doors and windows but not within 150 mm of the ceiling, and between 1 m and 3 m horizontally from the appliance.

Keep the boundary clear

An alarm is not a combustion test and its silence does not cancel symptoms or an analyser reading. Building-regulation alarm requirements and placement rules vary by jurisdiction and fuel appliance. Follow current Approved Document J and the alarm instructions for the installation.