Tech Notes

Compressed Air Quality and Oil Carryover

The compressed air quality that is needed is a critical element when it comes to compressor rentals. Different machines vary widely in terms of the purity of the delivered air.

Most rental equipment falls into one of three "air quality" categories:

1. Inherently oil-free compressors, which do not add ANY oil to the air being compressed;

2, Lubricated compressors with filtration, most of the oil added to the air during the compression process is removed via filtration.

3. Standard electric oil-flooded rotary screw compressors (which usually include aftercoolers) and Standard Construction grade portable compressors (which usually do not include aftercooling)..

The benefit of renting inherently oil-free compressors is obvious no oil in the air. But because they are truly oil-free, they rent for higher rates than lubricated compressors.

For applications that require oil-free compressed air, it is important to rent only inherently oil-free compressors, just as it is required to purchase them for your permanent installations.

The Instrument Society of America definition of "Instrument Quality" Air is:

  • A maximum oil content of less than one part per million (by weight)
  • The particle size in the air stream must be less than 40 microns; and
  • The dew point must be 18F below the minimum temperature to which the air is exposed



AirNow Industrial Compression Services
8150 North Central Expressway, Suite 1525
Dallas, Texas 75206
Phone: 1-972-861-1200