The Eaton tank breather filters "breathe" air in and out as the oil level rises and falls. The filters prevent the penetration of contamination from the ambient air in the hydraulic fluid. This circulating air contains articles and moisture that can cause corrosion, increase equipment wear, and reduce fluid performance. In typical systems, the internal hydraulic fluid is warmer than the external environment. This difference in temperatures causes water vapor to form. Breathers protect your hydraulic system by filtering out damaging moisture and particles.