Dr Porter said people should be aware that at the time of year when flu was most common carbon monoxide poisoning could be a potential cause of symptoms. Stomach pains Gas appliances such as fires, water heaters and boilers can be affected. If an appliance is leaking carbon monoxide, it is usually because it has been installed or maintained inadequately. There can also be problems if the flue is blocked, or there is no ventilation. Warning signs of a potential problem include sooty stains around the appliance showing carbon has escaped, a yellow or orange flame when it should be blue, and an odd smell when the appliance is on.
People can be particularly vulnerable if they leave a leaky gas appliance on while they sleep.
Appliances should never be covered, and flues, airways and ventilation should not be blocked.