Carbon monoxide poisoning from incomplete combustion, blocked flue or inadequate ventilation
risk assessment
A written risk assessment for carbon monoxide poisoning from incomplete combustion, blocked flue or inadequate ventilation on a UK construction site: who is at risk, what goes wrong, how likely and how bad before and after controls, and the control measures that bring the score down. Copy it into your RAMS and change what does not fit.
What goes wrong
Carbon monoxide poisoning causing rapid incapacitation and fatality; long-term neurological harm from sub-lethal exposure; RIDDOR reportable.
Control measures
- Flue and ventilation checked and confirmed adequate for the appliance before commissioning.
- Combustion performance analyser used to check flue gas readings on completion.
- CO alarm fitted and tested per manufacturer and Building Regulations requirements.
- Appliance not left in use if a spillage or flue fault is found, warning notice issued and gas supply capped at the appliance.
Where this sits in a RAMS
- The risk assessment names the hazard, who it can hurt, how badly, and what you will do about it. That is this page.
- The method statement then says how the work is actually done, step by step, with these controls built into the steps rather than listed at the end.
- The people doing the work read it and sign it before they start. Keep the signed copy with the job, and review it when anything changes.
Questions people ask
Do I need a written risk assessment for carbon monoxide poisoning from incomplete combustion, blocked flue or inadequate ventilation?
If you employ five or more people, the significant findings of your risk assessments must be written down (Management of Health and Safety at Work Regulations 1999, regulation 3). Below five it is still expected on any managed site, and every principal contractor will ask for it as part of your RAMS before you start. Guidance, not legal advice.
How is the risk score worked out?
Likelihood (1 to 5) multiplied by severity (1 to 5). This hazard scores 2 × 5 = 10 before controls (high) and 1 × 4 = 4 with the controls in place (low). The residual score is what you are accepting when you sign the RAMS off.
Can I copy this into my own RAMS?
Yes. It is written as a starting point. Change what does not match your site, add anything specific to the job, and make sure the person signing it off has actually read it. A risk assessment nobody edited is the first thing an inspector notices.
Who should carry out the risk assessment?
A competent person: someone with the training, knowledge and experience to recognise the hazards in that work and judge the controls. On most small sites that is the supervisor or the contractor themselves, with the people doing the job involved. Guidance, not legal advice.
How often should it be reviewed?
Whenever the job, the site conditions, the plant or the people change, after any incident or near miss, and at least annually so it does not go stale. Date every review.
Build the whole RAMS in ten minutes
Type the job and the trade, and SiteLynx drafts the scope, pulls hazards like this one from the library with their controls, lays out the method steps and puts it in front of your team to sign on their phones. Every plan is 14 days free.
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