The most basic analysis is the purely visual examination of a sample of fuel, during which the tell tale signs of contamination such as black gelatinous matter, small soft particles floating in the fuel, discoloured or hazy fuel. It is crucial to make sure that a representative sample is obtained from the bottom of the tank, to avoid being lulled into a false sense of security by a sample taken simply by dipping the top of the tank.

Specialist laboratories which carry out microbiological analysis of samples taken from fuel tanks should provide written reports of their findings, and certification, when requested. Microbiological analysis should include quantitative checks on the number of aerobic bacteria and fungal colonies present, and should also determine whether or not SRBs are present. A haze test on the fuel should also be carried out.

Dip slides provide a cheaper alternative to a full laboratory analysis, but they give less reliable results when fuel samples are involved. Nevertheless, they do at least provide an indication of the state of the fuel, and frequent use will show up any deteriorating trends. Treatment of Contamination >