BOREAL LASER GasFinderMC-2, Operation Manual

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9.7
Boreal Laser Inc. GasFinderMC Installation Manual — Appendices July 17th 2017
Appendix E — Conversion from ppm to mg/m 3
(Parts per million to milligrams per cubic metre)
To convert from ppm to mg/m
3
the following equation is used and follows the EPA Air
Emissions Monitoring Guidance Note #2 (AG1):
Concentration (mg/m
3
) = Concentration (ppm) x molecular weight (g)
molar volume (l)
In the following example Hydrogen Fluoride (HF) is used to illustrate the conversion:
HF
reading from GasFinder = 1ppm at STP*
Molecular weight of HF = 20.006 g/mole
At STP the molar volume of an ideal gas = 22.41 litres
Therefore the concentration = 1 x 20.006
22.41
1ppm HF = 0.8927 mg/m 3 at STP
*STP refers to:
Standard Atmospheric Pressure (P) = 101.325kPa
Standard temperature (K) = 273.15K
If the measurement is not taken at STP then an aditional correction is required to adjust to STP:
Concentration (mg/m 3 at STP) = Concentration (mg/m 3 ) x T x 101.325
273.15 P
where T is the path temperature (Kelvin)
P is the absolute path pressure (kilopascals)
eg. With a reading of 11 ppm, a path temperature of 30°C and path pressure of 94.34 kPa:
Actual Concentration = 11 x 0.8927 x 303.15 x 101.325 mg/m 3
273.15 94.34
= 9.8197 x 1.11 x 1.074 mg/m 3
11ppm of HF = 11.71 mg/m
3
.
Note : If the measured ppm values have already been corrected for pressure and/or temperature
using either the onboard compensation or the supplied compensation curves, then in the
above equation use T = 293.15K and/or P = 101.325kPa; not the sample measurement
conditions.