Standards stipulate 6-min time interval of averaging for measurements of radio-frequency electromagnetic fields to assess human exposure to non-ionising radiation. Having in mind the base stations of public land mobile systems, the time interval defined in such a way noticeably limits the number of measuring points in practical applications. In this paper, based on the results of measurements in the vicinity of a multisystem base station (Global System for Mobile Communications [GSM], Digital Communication System [DCS] and Universal Mobile Telecommunications System [UMTS]), it was shown that the measurement process can be significantly accelerated by using shorter time intervals of averaging--15 s, 30 s and 1 min. It was found that measurement results differed from the 6-min root-mean-square mean by 10.5 %, 15.9 and 19 %, respectively, while the uncertainty of the measurements was increased by 3.0 %, 3.8 and 4.4 %, respectively. Shorter time-averaging intervals would reduce the total duration of the exposure assessment survey, while not compromising too much on measurement quality.