Generally lubricants used in mechanisms, such as turbofan engines, are contaminated. Indeed a lubricating fluid can carry all sort of debris (in terms of size, nature and quantities) within lubricated contacts of rolling bearings for example. As avoiding such phenomena seems impossible, particle entrapment must be fully understood and widely investigated. A novel approach with a device combining a tribometer and a µ-Particle Image Velocimetry (µ-PIV) visualization system was developed. It allows the direct observation of the lubricant in the vicinity of the contact. Considering a glass-steel contact, it gives the possibility to get in-situ measurements on the dynamics of suspended fluorescent particles, which act as debris. In this study, particle trajectories are analyzed in order to observe how particles might bypass or be entrapped inside the contact.