What this means for your next step
Carbon monoxide cannot be detected by smell. If exposure is suspected, go outside and seek medical advice promptly; do not re-enter until advised. NHS 111 can advise on suspected symptoms. Call 999 for serious symptoms such as breathing difficulty, sudden confusion, collapse, weakness or chest pain. A routine service booking is not the immediate response.
When the property is safe and you are arranging follow-up or planned work, our carbon monoxide & combustion safety page explains the related service options. Use the coverage directory to check the enquiry route for your postcode.
Read the NHS guidance on suspected carbon monoxide poisoning for immediate medical steps.
Prepare a useful carbon monoxide warning signs enquiry
Send the essentials
Include the full postcode, appliance make and model, fault code, current heating and hot-water status, and the best contact number for access.
Make access clear
Explain tenant arrangements, parking restrictions and obstacles around the appliance, meter, controls or radiators so the visit can be planned properly.
Verify before work
Ask to see the Gas Safe ID card and check that the category listed on the reverse covers the appliance and task being discussed.
Related questions before booking
For another part of carbon monoxide warning signs, read Carbon monoxide warning signs: A practical homeowner guide before choosing the appointment scope.
For another part of carbon monoxide warning signs, read Carbon monoxide warning signs: What an engineer checks before choosing the appointment scope.

