Most hydraulic reservoirs feature a pocket of open space between the fluid level and the top of the reservoir. This open space, known as head space, fills with moisture as humid air ingresses via faulty seals, vents, and other entry points. The Headspace Dehydrator (HSD) tackles water contamination before it can contaminate your hydraulic oil by dehydrating the moist air within the head space before it can condense into liquid contamination.