Expert Home Safety: Carbon Monoxide

Carbon monoxide, the colorless, odorless gas is produced naturally by a number of different processes, but in the household, it typically comes from the incomplete combustion of fuel from heating and cooking appliances. Primary sources include leaking chimneys, furnaces, gas water heaters, wood and gas stoves, generators, tobacco smoke and exhaust from automobiles. Exposure to carbon monoxide beyond a low level is toxic, and depending on the level and longevity of the exposure can cause acute or chronic symptoms. Carbon monoxide from tobacco smoke competes with oxygen for the pigment in the blood known as hemoglobin. When the blood is short of oxygen, it can lead to suffocation and death.

Carbon monoxide (known chemically as CO) is most often formed when there is inadequate supply of air to support full combustion of a carbon fuel. It is colorless, odorless and very poisonous. It does not dissolve readily in water, but it does so in ethanol and benzene. The gaseous oxide melts at -199°C, and becomes a gas at -91.5°C and has a relative density of 1.25. Carbon monoxide is itself flammable and as a fuel component in a number of industrial processes. It has a molar mass of 28.0, making it lighter than air, which has a molar mass of 28.8. Production of carbon monoxide through combustion can be minimized by ensuring that the combustion occurs with an adequate supply of oxygen, which will produce carbon dioxide, a significantly less harmful gas.

The effects of carbon monoxide on human beings depend on the level and length of the exposure to the gas. At low concentrations, weakness and chest pain may occur. At higher concentrations, there are more serious symptoms such as nausea, headaches, dizziness and confusion. These effects occur when carbon monoxide takes the place of oxygen in the blood's hemoglobin, which normally carries the oxygen throughout the body. At moderate concentrations, exposure to the gas causes angina, impaired vision and reduced brain functionality. The concentration of carbon monoxide in well ventilated areas is between 0.5 and 15ppm while in poorly ventilated areas such as garages and kitchens with poorly adjusted stoves, the concentration can be more than 30ppm. Smoking causes exposure to carbon monoxide at a rate significantly greater than normal, and this exposure can be a major factor in the associated health risks. At concentrations greater than 665ppm, about 50% of the hemoglobin in the blood is converted to carboxyhemoglobin, which blocks oxygen distribution. This condition can cause coma, seizure and fatality.

Statistics show that more than 24,000 people are exposed to carbon monoxide annually in the UK while in the US the number is more than 100,000. Statistics in the US show that 310 people are exposed to the dangers of carbon monoxide poisoning each day. From this, about 1,360 people die every year in the US. In England, more than 500 patients were admitted in the hospitals between 2002 and 2003 for the treatment of acute symptoms of carbon monoxide poisoning.

The potentially deadly effects of carbon monoxide exposure can be avoided with a few simple safety measures. CO detectors sound an alarm when the concentration of carbon monoxide in the environment rises above a safe level. Proper ventilation and maintenance of wood and gas stoves, furnaces, and water heaters can all but eliminate the exposure to carbon monoxide in the household. Care should also be taken to prevent extended periods of idling of motor vehicles in garages. Even when open, garages can build up a significant amount of exhaust fumes.

More information about carbon monoxide and safety measures can be obtained from the following links: