Abstract: In view of coal seam condition, coal samples were divided into four categories according to there particle sizes. Based on the theoretical research on gas desorption speeds of coal samples with different sizes, the sampling conditions, sampling methods and sampling times of coal samples with different sizes were analyzed systematically according to the gas desorption data from field and laboratory measurement. Meanwhile, according to applicable conditions of mature sampling equipment and methods, such as coal barrel, pressure air ejector coal sampling equipment, reverse circulation plus wind pressure coal sampling equipment, and orifice connected with coal powder method, the suitable sampling technology and methods of coal samples with different sizes and sampling conditions were put forward, which can provide instruction for gas content direct determination in underground mine.

Key words: gas content direct determination method, gas content loss, coal sampling method, coal sampling time, coal sample size