the blood compartment side of the membrane an alternate embodiment of the present invention is constructed using hollow fiber microporous membranes instead of a flat sheet membrane referring to fig4 a hemolysis detector constructed according to this embodiment is shown in cross section as with the other embodiments thereis an outer shell 38 having a blood inlet port 40 and a blood outlet port 42 a blood compartment 44 and a plasma compartment 46 in contrast to theflat membrane of the previous embodiment however here are used a plurality of hollow fiber microporous membranes 48 identical to those used in blood cell plasma separation and known to those practicing in the art the hollow fibers number approximately 20 to 30 and serve to separatethe blood compartment bounded by the outer surface of the hollow fibers from the plasma compartment bounded by the inner surface of the hollow fibers in addition to the boundary formed by the hollow fibers there is an additional barrier between the compartments and its support means for the fibers such as potting compound 49 the remainder of the device is identical in function and similar in construction to the first embodiment having an elastic air sac 50 and plunger 52 to apply force on the air sac 50 against fixed member 54 in this embodiment the air sac neck and light path chamber are combined in a single element 56 the transmembrane pressure supplied by the squeezing of the elastic air sac transverses the path 56 longitudinally while the light generated by light source 58 traverses the pathway 56 before.