With growing economies leading to more intensive industry and manufacturing as well as terrorist threats, the need for fire service, emergency response and maintenance workers to be equipped with portable multi-gas detector has increased. Most environments where a team may enter need to be tested for a combination of toxic gases including carbon monoxide, hydrogen sulfide and oxygen depletion/enrichment as well as combustible gases including LEL (lower explosive limit) and UEL (upper explosive limit).
A standard multi-gas detector uses one sensor technology that ionizes the gas molecules with the help of a heated metal oxide semiconductor. The ionized molecules then pass through two charged plates creating an electric current between the plates that is proportional to the amount of gas present. This output is converted into a display reading for the user and is also logged for future reference.
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Most confined space entry instruments use this sensor but some use electrochemical sensors or PID (photometric infrared) sensors as well. For specialized applications, such as spraying a confined space with high concentrations of CO2 to drive out or euthanize pests such as rodents, bed bugs and cockroaches, a different type of carbon dioxide multi-gas detector is used. This instrument uses a highly accurate CO2 sensor and can record the data for future reference.
Many of these multi-gas detectors offer a range of optional accessories to allow customization to the specific needs of users such as a holster with pouch, a metal belt clip or an English manual. In addition, some instruments feature a backlight to illuminate the display in low light conditions and are equipped with alarm settings that take the presence of other combustible gases into consideration when alarming.