Leave, then call for help
Stop using suspected fuel-burning appliances if you can do so safely on the way out. Opening doors/windows or turning off appliances must not delay evacuation; do not go back inside to do these tasks. The original guide suggests completing tasks before leaving — safety takes priority over that sequence. From outside, call the free, 24-hour National Gas Emergency Service on 0800 111 999 for suspected gas-appliance carbon monoxide danger, and follow its advice. Do not re-enter or restart appliances until professionals confirm it is safe, even if you feel well or the alarm stops.
