However, Blue does not necessarily mean its safe. Get your appliances checked annually. Doing the same for you home is common sense as you spend most of your time there. Completely remove these obstructions from the flue area and fit a guard to stop any birds nesting. They can be particularly hazardous.
Older appliances can be problematic, use the electric toaster instead.
Get your cooker checked. Check your air bricks or trickle vents. If the appliances in your home do not have enough air they will produce carbon monoxide . Do it every year don t leave it to chance. Remember the engineer can only check the conditions on the day that he attends, get protection year round, fit a CO detector with a low level alarm .