1. PPM: volume concentration, said the volume of one million volume of air contained in the volume of pollutants;

2. %LEL: said the explosion limit units, gas detection products generally measured in the lower limit of a certain gas explosion;

3. %VOL: that the volume ratio of gas concentration, this unit is very large;

4. Common concentration units for example:

Methane gas :The upper limit of explosion % (V/V)  15.4

The lower limit of explosion % (V/V)   5.0

Example: 5.0%VOL=100%LEL=50000PPM

5. Other gas is also based on the conversion of the fourth;

6. Mg/m: said the quality of the pollutants and per cubic meter of air in the number;

7. The conversion format: mg/m³=M/22.4*ppm

ppm=（mg/m³）/（M/22.4）

8. M—gas molecular weight，ppm— volume concentration, T—temperature, Ba—pressure, and this is the standard algorithm, but in our actual work, can not consider the temperature and pressure, in order to facilitate the computation and memory, can refer to seventh items;

9. Portable gas detector to detect gas concentration is generally two detectors at the same time to detect, in order to get accurate detection data;

10. Portable gas detector must be used in a clean environment to open, to be stable after reading and then enter the environment to be seized.

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