Machines take in air at a very considerable rate. The average machine/engine inducts something like 9 or 10 m3 of air/litre the fuel burnt; hence the annual intake is in between 30,000 – 60,000 m3 of air per year. The content of contaminants in this air is likely to be 0.3 kg to o.6 kg, which in absence of filtration equipment/machine would all deposit in the engine where its abrasive nature would soon do serious damage. This corresponds to a dust concentration of 10 mg/m3 in air.
The inducted solids will accumulate as deposits on pistons, cylinder heads, valves and other components with a possibility of their being bonded in place by the oil film normally on these surfaces. The dust particle in the air will be washed out by the oil mist, to collect in the lubricant and then can be circulated through the machine. In Gas turbines too, the suspended solids will quickly wear away the turbine blades.
So the dust intake is very substantial, cannot be tolerated and filtration system must be installed to remove the dust. The sizing of the filter is selected based upon the amount of dust and size of dust particles. Since the filter will clog faster it will need cleaning or changing more quickly. Particles of sizes down to about 10 micron can do damage.
Filtration must also be provided to protect the machinery from such materials and the type will depend much on the nature of the machine being protected.