Abstract: A simple pass-fail tool that can be used to test the particulate contamination level in a fluid. The tool relies upon a comparison between a measured indicator of the contamination level in the fluid with another indicator of a contamination level of the fluid. Based on the comparison, conclusions about the contamination level of the fluid, and decisions about the fluid, for example that the fluid is acceptable for a particular use, can be made. The fluid can be fuel, lubrication, power transfer, heat exchange or other fluids used in a fluid system, for example fuel injection systems of diesel engines or hydraulic systems, where contamination of the fluid is of concern and use of an excessively contaminated fluid is to be avoided.