In the field of gas detection, lel%, vol%, and ppm are three commonly used units of concentration measurement, each with a specific meaning:
Lel% (Lower Explosive Limit%)Lel is the abbreviation of Lower Explosive Limit, which indicates the lowest concentration of flammable gas in the air that can cause combustion or **. lel% is a relative quantity used to measure the percentage of the volume concentration of a flammable gas in its ** range. When the concentration of combustible gas in the air reaches lel%, it means that the gas mixture is just in a state that can be ignited or **. For example, if the LEL of a flammable gas is 5%, it means that when the gas is in the air at 5% by volume, it can happen when it encounters an ignition source**.
vol% (volume percentage) vol% refers to the proportion of a gas in the total volume of a gas mixture, which is an absolute concentration unit that represents the percentage of the volume of a gas in the total volume. For example, if there is 2% oxygen in an environment, it means that 2 out of every 100 unit volume of gas is oxygen.
ppm (parts per million) ppm is a unit that expresses the concentration of trace substances, which means parts per million. In gas detection, 1 ppm is equivalent to 1 gas to be measured per million parts of gas. This is a very small concentration ratio and is often used to indicate lower concentrations of harmful gases or pollutants. For example, if a toxic gas has a concentration of 1000 ppm, it means that there are 1000 parts per million parts of the gas.
In the gas detector, lel% is generally used to detect the concentration of flammable and explosive gases to ensure the safety of the working environment; The vol% and ppm are more used for the quantitative detection of non-combustible gases or low-concentration gases, such as environmental monitoring, industrial hygiene and other fields. In practical applications, lel% and vol% are usually used for gas detection at higher concentrations, while ppm is suitable for monitoring toxic and harmful gases at low concentrations.