A microbial decontamination unit (A) has a door (B) which is hingedly mounted (90) to the housing. When the door is opened, the operator has access to a decontamination chamber (22), a mixing chamber (10) for receiving an anti-microbial solution concentrate, and other anti-microbial solution circulation paths (18). A mechanical locking mechanism (D) selectively locks the door member against a gasket (92) to assure that the anti-microbial solution does not leak between the door and the housing. The latch mechanism includes a hook member (54) that defines a circular bearing surface (52) that is rotatably received on a circular cam member (50). The circular cam member (50) is eccentrically mounted on a shaft (40). Rotation of the shaft and cam member moves a latch engaging surface (56) of the hook member into and out of engagement with a latch member (58) along an axis of travel (76). The cam member is selectively rotated a few degrees (78) past the axis of travel to provide an overcenter locking arrangement (FIG. 9 C). To open the door, the shaft is rotated the opposite direction first lifting the latch engaging surface off the latch member and then rotating an accelerator member (84) into the hook member. Continued rotation causes the accelerator member to rotate the hook member around the circular bearing (50) against the resilient bias force of a spring (70) (FIG. 9A).