The ASTM Specification for Aviation Turbine Fuel, D1655, requires the fuel to be "visibly free of undissolved water, sediment, and suspended solids" and the standard tests for contamination/particulate contamination are ASTMD2276/IP216 and D3830.
A known amount of fuel (typically 5 liters) is passed through standard 37 mm discs of 0.8 micron filter paper in the field. The discs are in plastic capsules or Tenite monitors, along with a 34mm diameter support pad.
The colorimetric test is used to qualitatively assess particulate contamination. In this test, one membrane is installed in the monitor in a field but in a clean area, and after testing, its color is evaluated against a standard scale to identify changes in fuel cleanliness.
This test is instantaneous and can be fully completed under facility conditions. This is especially useful for trending fuel purity, so membranes tested are dried and stored for later comparison.
The gravimetric test is used to quantify particulate contamination, and in this test, two prefabricated weight-matched membranes are embedded in the monitor under clean laboratory conditions. After testing, the laboratory reweighs the two membranes and determines the weight increase by subtracting the weight of the downstream membrane from the weight of the upstream membrane.
