Common unit conversion relationships and interpretation of frequently used nouns and terms

Common unit conversion relationships and interpretation of frequently used nouns and terms;

%LEL: It refers to the percentage of the lower explosive limit of flammable gas, expressed as a percentage. The lowest concentration at which flammable gas, when mixed with air, explodes upon encountering the minimum ignition energy. This unit is generally used for flammable gases, for example: Hydrogen (H2), carbon monoxide (CO), methane (CH4), ethane (C2H6), propane (C3H8), butane (C4H10), etc.

%VOL: It refers to the volume ratio concentration of a mixed gas, also expressed as a percentage. This is a general term used to describe the proportion of gas mixtures. It is often used to detect gases such as carbon dioxide (CO2), oxygen (O2), nitrogen (N2), and argon (Ar).

PPM: It is the abbreviation of part per million in English, indicating one part per million, dimensionless, the number of parts of a certain substance in a mixture of one million parts. Units commonly used for toxic and harmful gases, such as hydrogen sulfide (H2S), ammonia (NH3), hydrogen fluoride (HF), chlorine (CL2), etc.

1.Conversion between %VOL and PPM Since the meaning of %VOL is percentage and that of PPM is parts per million.the conversion relationship between them is very simple.1%VOL=10000PPM

2.Conversion between mg/m ³ and PPM,The value of mass concentration mg/m ³ will change with variations in environmental conditions such as temperature and air pressure (pressure).

In practical use, both temperature and pressure need to be measured simultaneously.
● mg/ M ³ =M/22.4×PPM×(273.15/(273.15+T))×P/101325
Here, M represents the molecular weight of the gas (g/mol), T represents the gas temperature (℃), and P represents the pressure (Pa).

Note: Under standard conditions, the molar volume of any gas is approximately 22.4L/mol.