1. Inherent contaminants are left when components are processed or when systems are assembled. Another kind of contamination is introduced when new fluids are injected into the system. An average of 100 gallons of new oil contains about 7 grams of pollution particles.

2. Open systems will absorb contaminants, and the usual ways of pollution absorption are: oil cylinders, open fuel tanks, regulating valves, hydraulic valves, and inappropriate breathing apparatus.

3. The oil cylinder is scratched or the piston rod dust ring is damaged is the most common source of hydraulic system pollution.

4. There is also a common pollutant injection system that is brought into the system during maintenance or repair.

5. The usual contaminants come from: pumps, valves, bearings and cylinders.

6. Common contaminants are those particles in the various components of the hydraulic system. Particle wear, adhesive wear, fatigue wear, corrosion wear, decomposition wear and erosion (rust) wear are common pollutants.