Objective: To study the correlation between the number of beds in the children's respiratory ward and the number of air colonies in the ward. Methods: A total of 4 wards with the same area in department of children's respiration were set as group A( 1 bed,2 escorts),group B( 2 beds,4 escorts),group C( 3 beds,6 escorts) and group D( 4 beds,8 escorts) respectively,and the other conditions remain the same. The plate exposure settlement method was used to sample and detect the number of air colonies in the ward...