Construction hazardous substances: Carbon monoxide

Carbon monoxide (CO) is a colourless and tasteless poisonous gas which can be produced in dangerous amounts when using  petrol powered equipment and gas appliances. Carbon monoxide can kill. This page tells you how to control these risks and why.

What you must do

The Control of Substances Hazardous to Health (COSHH) Regulations says you must protect against the risks from carbon monoxide. Follow the Assess, Control and Review model. Pay particular attention to:


Identify and assess: Identify those tasks/situations where significant levels of carbon monoxide may occur. This may include:


Prevent: Think about eliminating or reducing carbon monoxide risks. Use safer alternatives, such as electrical tools, where you can.  Never use petrol powered equipment indoors or in enclosed spaces unless the ventilation needs have been fully assessed. Seek expert advice to help you with this assessment. Specially selected mechanical extraction that vents to the outside will almost always be needed. Consider also:

Control: Even if you minimise some of the risk this way, you may still do  work that might create carbon monoxide. Control the risk by:

Train: Workers need to know how to use the controls properly. They also need to be aware of the signs and symptoms of carbon monoxide poisoning.


Supervise: Ensure that controls are effective and used by the workers.

Maintain: Properly maintain all equipment. LPG equipment can be particularly vulnerable. Blocked or partially blocked burners can lead to higher carbon monoxide levels and flame failure. LPG can also leak from damage to hoses etc.

What you should know

Carbon monoxide (CO) is a colourless, odourless, tasteless, poisonous gas produced by incomplete burning of carbon-based fuels like gas, petrol, wood and coal. Signs that indicate incomplete combustion is occurring and CO may be produced include;

CO stops your blood from bringing oxygen to cells, tissues, and organs. Early symptoms of CO poisoning can be confused with food poisoning, viral infections, flu or simple tiredness. They include drowsiness, headaches, breathlessness and nausea. CO levels can quickly kill without warning.

Updated 2023-04-11