or the like may be used to effect a seal between the top and the housing the integrity of the seal at each of end caps 16 and 18 is a function of the degree to which annular knife edges 40 and 44 compress the corresponding end cap initially such seal is usually very effective this seal depends upon several variables the resiliency of the end caps to maintain compressive engagement with the corresponding annular knife edge the resiliency of filter element 14 to bias the end caps against their respective annular knife edges and the properties of the fluid being filtered to induce deterioration of the resilience of the filter cartridge components fig2 illustrates a filter cartridge 10 and housing 12 similar to that shown in fig1 and representative of prior art embodiments that is it in includes annular knife edges 40 44 sealingly cooperating with annular end caps 16 18 in some applications an ultra violet lamp is disposed within the filter cartridge to irradiate with ultra violet radiation filtered fluid flowing into axial cavity 20 to protect the ultra violet lamp a sleeve 60 is disposed within axial cavity 20 in general radial alignment with filter cartridge 10 this sleeve houses the ultra violet lamp and may be made of quartz or similar material transparent to ultra violet radiation an annular spacer 62 or the like may be employed to maintain the displacement between sleeve and the filter cartridge necessarily the sleeve is sealed by.