A countertop decontamination unit (A) has a decontamination chamber (10) for receiving a tray or module (C) which contains items to be sterilized, disinfected, or otherwise microbially decontaminated. The tray or walls of the decontamination chamber itself provide fluid outlets from which an anti-microbial solution is conveyed through tubing (76) to fittings (78). A pump (20) recirculates the anti-microbial fluid. The fittings include a porous sleeve (80, 92) which is received in firm frictional connection with an annular surface of a bore, nipple, or coupler mechanism of the item (86) to be sterilized. The porous sleeve is preferably elastomeric when used for frictional interconnections, but may be rigid when used with threaded or other standardized connectors. The porous sleeve has a porosity of 3 microns or more, sufficient that the anti-microbial fluid penetrates through the porous portion and contacts the immediately contiguous and abutting annular surface. The porous member permits sufficient quantities of solution to contact these surfaces to assure they are microbially decontaminated. Associated surfaces that contact the item and can potentially trap microbes are also constructed of porous material. Other associated porous structures include porous closures, such as plugs (124, 160) or caps (120, 122) which close some of the access ports to the interior passages of endoscopes, item retainers (68), a bottom wall portion (62), other surfaces of the item (174), and the like.