My neighbours have just returned to their own house. Mother, father, daughter and son (home from uni) and both dogs. They were just settling down after their dinner to watch TV when their CO detector went off.
They came to us to see what to do. I told them to open all windows and doors and call the gas emergency services and to stay with us until the all clear. They arrived within 30 minutes and spent an hour dismantling their gas fire and checking the house had cleared of gas, before allowing them home.
This fire had been passed as safe during the summer, but as the gas man pointed out, this only means it was safe at that time, Faults can develop at any time.
I dread to think what could have happened if they had just settled down watching TV and this odourless gas had overcome them. The daughter is just recovering from heart surgery.
I hope this encourages others to check their CO monitors are working - if indeed you have one at all.