This document discusses fluid system contamination control. It explains that keeping fluid systems clean through filtration can increase bearing life by 5-20 times and decrease maintenance costs. It introduces ISO cleanliness standards for measuring particulate contamination levels. Target cleanliness levels are recommended for different system components based on operating pressure. Common sources of contamination include built-in contaminants from manufacturing, ingressed contaminants through seals and breathers, and generated contaminants from metalworking processes. Maintaining clean fluid helps maximize system reliability and uptime.