Abstract: A device (10) for removing contaminants from truck air systems or the like includes an assembly including a desiccant canister (100), a carrier (46), and a bottom closure (28) vertically removable in a passage (14) of a collar (12) mounted to the truck. The carrier (46) includes a horizontal plate (48) which divides the passage (14) into a coalescing chamber having a horizontally orientated, tubular coalescing filter (98) extending vertically above and diametrically over the sump including an electrically actuated purge valve (42) of the bottom closure (28). Air is directed vertically downward from the filter (98) by vertical legs (62) extending down from the horizontal plate (48) and on opposite sides of the filter (98). A follower plate (118) is biased in the canister (100) against the desiccant beads (116) by a wave spring (140) sandwiched thereagainst by a slideable retainer (142) fixed in the side wall (104) of the canister (100).