Abstract: Despite the great differences of geological structure of coal-bed,mining manner and working condition in coal mine in various areas of our country,the air in coal mine has a lot of coal dust,involve PM10 particles that can exist long time in air and its diameter less than 10 μm.These particles will affect resistance value of ionization chamber as same as particles of fire fog.The paper calculated the "base fog value" of ionic smoke inductor aroused by PM10,and the conclusion from the calculation was elicited that the ionic smoke inductor can be used in coal mine to forecast fire.And a mine-used ionic smoke inductor was successfully developed with MC145018.