The distribution of the gas humidity and temperature is an important factor influencing the process of coating particles in a fluidized bed. Reported are profiles based on experimental results for a top spray particulate coating using a single non-submerged spray nozzle. The profiles indicate that during the process,pockets of low temperature and high humidity are formed deep inside the bed. Associated with these pockets are regions of high temperature and humidity fluctuations. The profiles also show that the lowest gas temperature is located at the topmost part of the bed directly below the nozzle. The region of low temperature extends inwards giving rise to one of the two general shapes formed by the profile. Also, inside the bed, a region with highest gas temperature is formed, with its general shape depending on the shape of the temperature profile. The areas of the bed below the highest temperature region have a stable and constant gas temperature and humidity. The shape of the profiles are used to reveal the net circulation pattern of the particles. Using the profiles, four different zones with different coating functions were also identified. From the size of the zones, an optimum bed size for the given operating conditions can be deduced. (C) 1998 Elsevier Science S.A. All rights reserved.