After three years, the reduction in reflectance values slows down noticeably and the reflectance values of very clean and clean rooms increasingly turn into a constant value. For medium and highly soiled rooms, this generally does not apply. The room maintenance factor is dependent on the luminaire’s illuminance distribution (direct, direct-indirect or entirely indirect) and marginally also on room size. The following tables (a) to (i) contain the room maintenance factors according to CIE 97.2 amended by values for very clean rooms according to experience as well as measured values which are extrapolated for maintenance intervals of up to 6 years.