Designs are provided to reduce the possibility of contaminant particles with a large range of sizes, materials, travel speeds and angles of incidence reaching a particle-sensitive environment. According to an aspect of the disclosure, there is provided an object stage comprising first and second chambers, a first structure having a first surface, and a second structure. The second structure is configured to support an object in the second chamber, movable relative to the first structure. The second structure comprises a second surface opposing the first surface of the first structure thereby defining a gap between the first structure and the second structure that extends between the first chamber and the second chamber. The second structure further comprises a third surface within the first chamber. The object stage further comprises a trap disposed on at least a portion of the third surface, the trap comprising a plurality of baffles.