In order to predict and control asbestos concentration in rooms with asbestos − containing mate ． rials it is necessary to know its generation rate caused by direct or indirect d孟sturbance of the sprayed asbestos surface ， Various kinds Qf experiments we τe carried out 重 n a room with a ceiling containing asbestos ． Some disturbances occurred on the moistened flool expecting nQ redlspersion of asbestos might occur from it ． Main results obtained we エe as follows： 1． Hitting a ball to asbest σs ceihng