The bulk of all contaminants will be dissolved in the Compressor Oil of an operating System.
"The Easy Oil Test" (Detector Tube Method) offers a more definitive way to check the condition of any Compressor Oil or to pretest any stock Oil before it is to be added to a system.

The Checkmate body is connected on the suction side of a running system. Insert the oil detetcor tube and milk the system for a small amount of oil returning with the suction gas. The oil is allowed to collect on the indicating layer of the detector tube where a color change will occur. One of 6 different possible color changes will occur. The color change may indicate Acid, Moisture or a combination of both. A pass/fail color chart is provided to diagnosis the condition of the oil.

Please request literature and complete instruction manual before ordering this product.