Compressed Air Contaminants
Compressed air contaminants can be in the form of solids, liquids, or vapors. Contaminants can enter a compressed air system at the compressor intake, or can be introduced into the air stream by the system itself.

Air quality class is determined by the maximum particle size, pressure dewpoint, and maximum oil content allowed. For more information, see ISO 8573-1 Compressed Air Quality Classes in the Compressed Air System Best Practices Manual.

One of the main factors in determining air quality is whether lubricant-free air is required. Lubricant-free air can be produced either by using lubricant-free compressors, or with lubricant-injected compressors and additional air treatment equipment. The following factors can help one decide whether lubricant-free or lubricant-injected air is appropriate:

• If only one end use requires lubricant-free air, only the air supply to it should be treated to obtain the necessary air quality. Alternatively, it may be supplied by its own lubricant-free compressor. If the end uses in a plant require different levels of air quality, it may be advisable to divide the plant into different sections so that air treatment equipment that produces higher quality air is dedicated to the end uses that require the higher level of compressed air purification.
• Lubricant-free rotary screw and reciprocating compressors usually have higher initial costs, lower efficiency, and higher maintenance costs than lubricant- injected compressors. However, the additional separation, filtration, and drying equipment required by lubricant-injected compressors will generally cause some reduction in system efficiency, particularly if the system is not properly maintained.

Careful consideration should be given to the specific end use for the lubricant-free air, including the risks and costs associated with product contamination before selecting a lubricant-free or lubricant-injected compressor. Centrifugal compressors also offer an alternative for plants whose end uses require lubricant-free air.

FOR ADDITIONAL INFORMATION, PLEASE CONTACT:
EERE Information Center 1-877-EERE-INF (1-877-337-3463) www.eere.energy.gov
Industrial Technologies Program Energy Efficiency and Renewable Energy U.S. Department of Energy
Washington, DC 20585-0121 www.eere.energy.gov/industry