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Mine Ventilation and Environmental Hazards - Question from AMIE 2016 exam

The analysis of a sample of air from old workings is reported to be O2 – 19.3%, CO2 – 0.4%, N2 = 79.8%, CH4 – 0.5%. Find the percentage of air and black damp in the sample, as well as composition of black damp.

Standard composition is not given. These values can be taken as CO2 – 0.03, O2 – 20.93 and N2 – 79.04 respectively (if not given).

CO2 eq = CO2 wrt O2

\( = \left( {\frac{{C{O_{2,std}}}}{{{O_{2,std}}}}} \right){O_{2,ret}} = \left( {\frac{{0.03}}{{20.93}}} \right)x19.3\)

= 0.028

N2 eq = N2 wrt O2

\( = \left( {\frac{{{N_{2,std}}}}{{{O_{2,std}}}}} \right){O_{2,ret}} = \left( {\frac{{79.04}}{{20.93}}} \right)x19.3\)

= 72.88

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