Wood pellets have been widely used for power generation and domestic heating recently to substitute fossil fuels. For health and safety reasons, particle degradation and dusts generation in material storage and handling processes are always a serious concern for anyone involved. Also the level of fines in wood pellets can strongly influence fuel milling and combustion. For previous study, wood pellets attrition subjected to its mechanical properties has been reported. However pellet mechanical properties can be inconsistent and influenced by environmental conditions such as humidity, temperature and storage time. In this paper, attrition behaviour and dust generation of two types of wood pellets have been studied, which the pellets were stored in a constant relative humidity environment for a period of time (4 days). Physical properties such as moisture contents, bulk density and flexural stress of the pellets were measured for the pellets conditioned in a RH chamber, which was believed that equilibrium condition was achieved. Correspondingly, the conditioned pellets for a number of different humidity levels were tested for both impact test and dustiness test. The study shows that the pellets can lose structural strength due to in taking moisture from environment for a high relative humidity. Also a high humidity can result in an increased level of pellet degradation and dusts generated.