Related Terms of Gas Detector

1.Standard Gas: gases with known concentration,accuracy and composition.

2. Zero Gas (Fresh Air): pure air or nitrogen which is not containing measured gas or other interfering gas.

3.Explosive Range: the range of concentrations resulting from an explosion caused by ignition in the mixture gas of combustible gas and air.

4. Lower Explosive Limit (LEL): the lowest concentration resulting from an explosion caused by ignition in the mixture gas of combustible gas and air.                  

5. Upper Explosive Limit (UEL): the highest concentration resulting from an explosion caused by ignition in the mixture gas of combustible gas and air.

6. Maximum Allowable Concentration (MAC) :maximum allowable concentration of toxic gas in the air of the workplace.

7. Short Term Exposure Limit (STEL): A highest concentration of harmful substance that will not affect worker’s health,even if they are exposed to harmful substance for 15 minutes.

8.Time Weighted Average( TWA): A weighted average concentraion of harmful substance that will not affect worker’s health,even they repeatedly exposed to harmful substances 8 hours a day.

9. Immediately Dangerous to Life or Health Concentration(IDLH):A concentration that can cause fatal or permanent damage of health or an immediate loss of ability to escape.

Measurement Units of Common Gas Detection

1.molar volume of gas:symbol Vm, is the volume occupied by one mole of a substance at a given temperature and pressure,and it has two units:L/mol or m3/mol.

　The volume of any gas occupies one mole in the standard condition(0℃，101KP).

2、Vol%：concentration volume ratio of mixture gas

3、%LEL： percentage of lower explosive limit for combustible gases.

4、ppm：parts per million

5、ppb：parts per billion

Conversion of Gas Measurement Units

1.conversion of VOL% and %LEL

Formula:%LEL=(V÷LV)×100   /  Vol%=(L×LV) ÷100

V: known concentration volume ratio of combustible gas,%VOL 

LV:corresponding concentration volume ratio of 100%LEL combustible gas,%VOL

L:know lower explosive limit of combustible gas.%LEL

2.conversion of %LEL and ppm

Formula: ppm =(L×LV)×100  /  ％LEL=PM ÷(LV×100)

PM:know gas concentration,ppm；   

L：know lower explosive limit of combustible gas.%LEL；

LV：corresponding concentration volume ratio of 100%LEL combustible gas,%VOL

3.conversion of mg/m3 and ppm

Formula:ppm=(22.4×MG) ÷formula weight  / mg/m3=0.041×PM×formula weight

MG：known mass of gas；

mg/m3：formula weight—— molar mass of known gas，g/mol。

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