They are generated when natural gas does not get burned completely, because of an inadequate oxygen supply. These carbon monoxide fumes are very poisonous and can quickly kill. Inhalation of even small quantities can lead to a variety of serious health problems, including brain damage.
Warning signs of carbon monoxide poisoning include headaches, nausea, chest pains, sudden faintness, erratic behaviour, and diarrhoea or stomach pains. Carbon monoxide is most likely to be produced from gas appliances that are badly installed, not regularly maintained, or which do not have sufficient ventilation.
