71. In an underground coal mine area the graham's ratio found 3% is the indication of
72. A man exhales 0.002 m3 of CO2 per min when working in a confined space in underground. Assuming that the fresh air contains 0.03% CO2, the minimum quantity of fresh air to be supplied per person in m3/min, so that concentration of CO2, in air never crosses 0.4%, will be
73. The thermometer bulb covered with moist cloth called as
74. In a mine ventilation system, the resistances of two splits A and B are 0.5 Ns2m-8 and 2 Ns2m-8 respectively. Combined resistance of two shafts and trunk airways is 0.7 Ns2m-8. A quantity of 20 m3/s of air passes through split A. The total air power of the ventilation system in kW are
75. CO2 is best suited for extinguisher
76. A gas mask does not include
77. In a longwall panel, the main gate road is 1000 m long, 4.5 m wide and 2 m high. The gate road is to be used for airflow at the rate of 17 m3/s. Considering a coefficient of resistance of airways of 0.01, the pressure in Pa required to maintain the airflow in the gate road is
78. The early indication of spontaneous heating of coal can be given by
79. Quantity of air to be circulated to u/g workings where 150 worker employed in a largest shift and daily production 500 te will be
80. The chemical protosorb used in
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