Deposit formation poses severe hazards and negatively affects the functionality of pneumatic powder transport systems. A novel test-rig was developed for the measurement of the deposition of polymethyl-methacrylate powder in a horizontal, turbulent flow through a duct of a square cross-section. The parameters under investigation are the particles' size, shape, and mass flow rate, the conveying air's Reynolds number, relative humidity, and temperature, and the duct material. A continuous weighing method is used to quantify the particle deposition and resuspension rate and a Faraday cup is positioned at the duct outlet to measure the specific powder charge. For the considered conditions, the air humidity exhibits a strong influence, especially on the smallest particles. For small particles, a high charge even leads to deposition at the ceiling of the PC duct. Larger particles tend to settle at the center of the duct and smaller ones preferably at its corner. (C) 2020 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.