1. Boiler (only if it is on)
  2. Cooker (only if it is on)
  3. Fire (with the cat curled up in front of it)
  4. Generator in the garage (if it is working – at the moment it is just being stored)
  5. Car (again, as above with the generator and boiler, only if the engine is on).
  6. Barbecue through the window (but OK as long as used outside)
  7. Camping lantern on the kitchen cabinet (only if it is being used, ie. lit)

Please note that the electric fire would not burn anything so would not emit CO. There has been one case of CO from an electric night storage heater due to a blanket being put behind it and getting so hot it started to smoulder and burn.