Tubular daylight guidance systems were developed to introduce daylight into the building's core. Operating the system in desert climate regions, where both solar irradiance and dust resources are abundant, exposes them to dust accumulation that significantly reduces the system's efficiency. An experimental investigation was conducted in Cairo to understanding dirt accumulation patterns and impact, and to recommend suitable cleaning procedures. It was found that dust accumulation during three rainless periods, of 44 days each, could reduce the illuminance transmittance by up to 38%. The dust accumulation was found to decrease the system efficiency in a near-linear fashion with a 0.5% daily reduction. The highest illuminance transmittance magnitude and ratio were observed at midday, followed by the morning period and then the afternoon period. Similarly, the transmittance loss by the end of the experiment was found to be around 31%, 26% and 13% at noon, morning and afternoon respectively. It was found that the transmittance loss under a clear sky is up to 25% more than that under a cloudy sky. Further work needs to be done to examine other meteorological factors. Based on the study findings, it is recommended to clean the solar devices bimonthly to restore the system's efficiency. (C) 2021 Elsevier Ltd. All rights reserved.