Carbon Monoxide
Carbon monoxide, an odorless, poisonous gas, can be generated by gas furnaces and water heaters, ranges, space heaters, or wood stoves if they are malfunctioning or not vented properly. Cars, portable generators, and gas-powered gardening equipment also generate carbon monoxide (CO) and can cause problems if they are operated in enclosed areas or attached garages. Once inhaled, carbon monoxide inhibits the blood's ability to carry oxygen by replacing oxygen in the red blood cells which prevents the oxygen supply from reaching the organs in the body. This oxygen deprivation can cause varying amounts of damage depending on the level of exposure. Low level exposure can cause flu-like symptoms including shortness of breath, mild headaches, fatigue, and nausea. Higher level exposure may cause dizziness, mental confusion, severe headaches, nausea, and fainting. Prolonged high level exposure can cause death. According to the U.S. Consumer Product Safety Commission, more than 2,500 people will die and 100,000 will be seriously injured by carbon monoxide over the next 10 years.
In the 1300s, Arnold of Villanova (1235-1311), a Spanish scientist, noticed that poisonous fumes were produced when wood was burned without adequate ventilation. Wood and other fuels containing carbon--such as coal, oil, and gasoline--produce carbon monoxide when they are burned without enough oxygen. (If enough oxygen were present, carbon dioxide, or CO2, would be formed instead..) Although Arnold of Villanova did not understand the chemistry of carbon monoxide formation, he was the first to call attention to its harmful effects.
During the 1600s and 1700s, scientists began to learn more about the nature of gases. In the 1770s, oxygen and many other gases were discovered, and chemists determined what part gases play in the process of combustion, or burning. During this period of discovery, French chemist Joseph Marie François de Lassone (1717-1788) and British chemist Joseph Priestley independently prepared carbon monoxide gas in the laboratory for the first time. Soon afterward, in 1800, British chemist William Cumberland Cruikshank (1745-1800) determined its chemical composition.
However, carbon monoxide's poisonous effects were not well understood until the 1850s, when Claude Bernard, a French physiologist, explained how the gas acts in the human body. Bernard showed that when we breathe carbon monoxide, the gas prevents our blood from carrying oxygen through the body. It does this by combining with the blood's oxygen-carrying substance, called hemoglobin. Because carbon monoxide's affinity for hemoglobin is much stronger than that of oxygen, the bloodstream immediately absorbs carbon monoxide, and the body becomes starved of its life-supporting oxygen.
During the 1800s, chemists first attempted to turn gases into liquids. The first gas was liquefied in 1823 but it was not until 1877 that Louis Paul Cailletet, a French physicist, was able to liquefy carbon monoxide. To accomplish this, Cailletet simultaneously compressed and cooled a sample of carbon monoxide and then allowed it to expand. As it expanded, the gas cooled radically and condensed into a small amount of liquid.
Normally, carbon monoxide is present in the air in extremely minute amounts—not enough to pose a threat. However, in large cities, unhealthy amounts of carbon monoxide can build up, especially during heavy rush-hour traffic. Cars that are old give off the most carbon monoxide. Modern cars are equipped with catalytic converters that chemically change carbon monoxide into carbon dioxide. Despite its dangers, carbon monoxide is useful to industry as a fuel gas, which provides heat for manufacturing processes, and as a raw material for making chemicals and purifying such metals as iron and nickel. Over the last few decades technology has been developed to detect carbon monoxide for industrial applications. For example, the chemical industry has used a number electronic gas sensors for analytical applications. Early industrial sensors involved a dual chambered sensor which oxidized CO and compared the heat of oxidation from the test chamber to a reference chamber. This type of oxidation requires a special platinum oxide catalyst and a heat source to burn the carbon monoxide. These systems were unacceptable for home use due their complexity of operation, expense, and lack of sensitivity. However, in the last decade or so, home carbon monoxide detectors have been made possible by improvements in advanced gas sensing technology. Other key factors have also contributed to the increased popularity of CO detectors. One is the rise in the use of other home safety appliances, such as smoke alarms. Another is the increased awareness of the dangers of carbon monoxide. Today, relatively inexpensive CO detectors can be purchased for as little as $30 to $80. In fact, many cities are now requiring that at least one smoke detector be installed in every home, apartment, and hotel.
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