Surface Environment, Mine Ventilation and Underground Hazards · Underground Hazards · 2 marks · Numerical answer
Mine-air analysis gives O₂17.15%, CO₂3.40%, CH₄2.20%, N₂77.25%. Atmospheric air has O₂20.95%, CO₂0.03%, N₂79.02%. Find blackdamp percentage, to two decimals.
Use the oxygen content to identify the fresh-air fraction:17.15/20.95=0.818616. That fraction supplies the matching atmospheric nitrogen/carbon dioxide. The residual mixture after subtracting fresh air and methane is blackdamp:100−81.8616−2.20=15.9384%, or 15.94%. Methane is treated separately from blackdamp.
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