A carbon monoxide alarm is a device present in many structures, particularly homes, that is used to detect carbon monoxide levels in the air and to warn the inhabitants of the building when carbon monoxide levels are dangerously high. Carbon monoxide can be very deadly because it has no odor or color; it is undetectable without the help of a carbon monoxide alarm or some other form of detector. When inhaled, carbon monoxide enters the bloodstream and binds to hemoglobin, a protein that is normally used for oxygen transportation. Carbon monoxide prevents oxygen from binding to the hemoglobin, resulting in an inadequate supply of oxygen reaching the organs in the body. The use of a carbon monoxide alarm is one simple preventative measure that greatly reduces the risk of carbon monoxide poisoning.
Carbon monoxide alarms can be acquired easily and at minimal expense. Some governments, particularly at regional levels, even require carbon monoxide detectors to be installed in houses during construction. The alarm units require almost no maintenance; some have batteries that need to be replaced after a period of five years or more, while others can be powered by the building's electrical system. Unlike smoke detectors, carbon monoxide alarms do not necessarily need to be installed near the ceiling because, unlike smoke, carbon monoxide has approximately the same density as air and tends to be evenly spread throughout the air. Some smoke detectors actually include a built-in carbon monoxide alarm, removing the need to have two separate devices.
There are many different methods through which a carbon monoxide alarm can detect the presence of carbon monoxide in the air. Some contain a synthetic version of hemoglobin; an alarm sounds when carbon monoxide binds to it. Others contain electrochemical cells that respond to changes in the concentration of various gases in the air. Semiconductors are also sometimes used as carbon monoxide alarms, but electrochemical cells tend to perform appreciably better.
It is important for a carbon monoxide alarm to be able to communicate the presence of high levels of carbon monoxide to the inhabitants of a structure. The traditional method of doing so involves a loud alarm, but this can sometimes be ineffective for heavy sleepers or for people with poor hearing. In such cases, a carbon monoxide alarm may be wirelessly connected to strobe lights or to a vibrating pad inside of one's pillow. These overlapping measures ensure that one is able to respond quickly to a threat from carbon monoxide.