Wood burning stoves 'can cause lethal carbon monoxide poisoning' warns HPA Rooms in which appliances are used must also be adequately ventilated. CO is produced when fossil fuels burn without a good supply of air. If that happens in a room without adequate ventilation, levels can build up dangerously. The gas binds to haemoglobin in the blood 200 times more readily than oxygen, so inhaling high levels can quickly starve major organs like the heart, brain and nervous system of oxygen. A mild case of CO poisoning can just cause a very bad headache, but if someone is exposed to high levels of CO for too long, they can fall unconscious and die within minutes. In addition to the deaths, the HPA said some 4,000 people need to be treated in accident and emergency for CO poisoning. Although most were not sick enough to be admitted to hospital, long term exposure to CO has been linked with neurological effects such as having difficulty concentrating. The HPS is also advising that all households should have an audible carbon monoxide alarm which met European standards. Dr Harrison said telltale signs of carbon monoxide emissions included "black sooty marks" on the wall around stoves, boilers or fires, or on the clay radiator bars of gas fires, and smoke accumulating in rooms due to faulty flues. Another sign was yellow flames on gas appliances that were meant to have blue flames. Wood burning stoves have become very popular in Britain, due to their green credentials and rising fuel prices. Previous research has suggested that they could feasibly be a cancer risk, if they are not fitted properly and particulates [very small particles] escape into the home. However, the Solid Fuel Association says there is very little chance of fumes, including CO and particulates, escaping from a properly fitted device.