The combustible gas indicator is designed to measure combustible gas or vapor content in air. This instrument is capable of detecting the presence of any gas or vapor which, when combined with oxygen in free air, presents a potential hazard due to flammability/explosion. The combustible gas indicator will not indicate the combustible gas content in atmospheres containing less than 10% oxygen.

The combustible gas indicator is an instrument used to detect various flammable gases and vapors. Combustible gas indicators are made by several manufacturers. Although they all operate on the same general principles, they vary in certain details. Each indicator is accompanied by a complete set of operating and maintenance instructions. In addition, a condensed operating routine is attached to the inside of the case cover. Before using any combustible gas indicator, read the instructions carefully.

A combustible gas indicator employs a heated platinum-wire filament associated with a Wheat-tone bridge or modified potentiometertype circuit. The combustible gas indicator can quickly, safely, and accurately detect all combustible gases or vapors associated with fuel oils, gasoline, alcohol, acetone vapors, illuminating gas, fuel gas, hydrogen, and acetylene in mixtures with air or oxygen. The indicator can detect small quantities of these gases or vapors up to the lower explosive limit (LEL). It gives a reliable indication of the mixture if it is in the upper explosive range or beyond the upper explosive limit. The higher and lower explosive limits define the range of a concentration of a material, expressed in the percent in the air, that will burn or explode if ignited. The LEL is the minimum percent by volume of a gas that, when mixed with air at normal temperature and pressure, will form a flammable mixture. The higher explosive limit (HEL) is the point at which an explosion is certain. The combustible gas indicator does not identify combustible gas or gases; it merely indicates that one or more combustible gases are present in a certain proportion.

Many industries, including the petroleum industry use a combustible gas indicator, which is a device used to detect the presence of flammable or combustible gases in an environment. There is a flammable limit for every gas, and a combustible gas indicator tests for this limit in the gas vapors in an environment. To do so, the indicator requires sufficient amount of oxygen so as to detect the LFL (lower flammable limit) of gas in the air. The indicator has a needle set on it that takes the reading, starting from a 0 to far right back. If the indicator gives off a reading of 10% and above, then the atmosphere is potentially combustible.


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