The room surface maintenance factor RSMF takes into account the reduction of luminous flux due to the soiling of the room surfaces. It signifies the ratio of the room surface reflectances before and after cleaning. The RSMF depends on the degree of soiling of the room or the ambient conditions of a room and the specified cleaning frequency. Further influencing factors are the size of the room and the type of lighting (direct to indirect emission).
The room surface maintenance factor consists of four classifications for room surface deterioration: P pure (very clean room), C clean (clean room), N normal (average conditions) and D dirty (dirty room).