Safety and the Law · 4 lessons
Smell gas? What to do, and carbon monoxide
Everyone should know these actions, engineer or not. The path teaches them first because they matter most.
Our gas engineering path is in public beta: some lessons are still being checked. More sections are coming.
If you smell gas
No switches, flames or cigarettes. If it is safe and quick, open doors and windows and turn the gas off at the emergency control valve, never going into a cellar to reach it. Get out and call from outside: 0800 111 999 in Great Britain, 0800 002 001 in Northern Ireland, the supplier's line for LPG, or 999 if anyone is in danger.
Carbon monoxide gives no warning smell
CO has no colour or smell. Headaches, dizziness, nausea or flu-like feelings can be signs, as can unexpected yellow flames, soot or staining. Get to fresh air, get urgent medical advice and call the gas emergency service.
Alarms differ by nation
England, Wales, Scotland and Northern Ireland each set their own carbon monoxide alarm rules, which also depend on the kind of home. An alarm never replaces servicing or a safety check.
An unsafe appliance stays off
When an engineer finds an unsafe situation, they explain the risk and may ask to turn the appliance off or disconnect it. It stays unused until it is repaired and proven safe; never remove a warning label.
The lessons this guide comes from
- Smell gas: leave and call
- Carbon monoxide signs and symptoms
- CO alarms by nation
- Unsafe situations
Keep learning
Sources
Sources checked 29 October 2026. The law and official pages can change.
- HSE: carbon monoxideCarbon monoxide symptoms and causes.
- HSE: domestic gas safety FAQsGas Safe registered engineers in homes; checking an engineer's ID card.