In his 1967 book, “The Use of Lateral Thinking” Edward di Bono introduced the concept identified in the book’s title. He contrasted “lateral thinking” against “linear thinking” and argued that successful resolution of any challenge required both types of thinking. What does this have to do with detecting microbes in fuel systems. Standard Practices, such as PEI’s RP900 “Recommended Practices for the Inspection and Maintenance of UST Systems”, are examples of excellent linear thinking. They prescribe a series of steps for performing UST system condition monitoring. Similarly, ASTM D4057 “Practice for Manual Sampling of Petroleum and Petroleum Products” provide a wonderful, linear sequence of steps for collecting fuel samples. Neither of these documents promotes lateral thinking. RP900 is great at detecting component failures once they occur. Similarly, D4057 is great for obtaining samples on which to run tests to determine whether the product is in specification. In contrast, ASTM D7464 “Practice for Manual Sampling of Liquid Fuels, Associated Materials and Fuel System Components for Microbiological Testing” encourages lateral thinking. It encourages users to ask: “what do I intend to do with my sample” and “if I want to detect microbial contamination, what kind of sample do I need to collect; from where should I collect that sample?”
Samples collected per D4057 are unlikely to contain microbes. Consequently, they are not the samples on which it makes any sense to test for microbial contamination. This is the number one reason microbial contamination in fuel systems remains undetected even after the bugs have caused component failure. Microbes need free-water to thrive. Free-water accumulates as condensate on tank surfaces – particularly in the headspace, above product, and on the tank bottom, below product. A substantial volume of free-water is also trapped within slime that accumulates on tank walls. Linear thinking guides us to collecting UST bottom-samples from fill-lines. Lateral thinking helps us to consider alternative sampling points and sample types. If you are interested in learning more about sample collection for microbiological testing, contact me by phone (609.716.0200) or email ( In my next blog post, I’ll discuss microbiological test methods.