Representative samples of fuel products and associated substances are required for the determination of microbial contamination in fuels and fuel systems in order to accurately assess the biodeterioration risk posed to the fuel, fuel-system components or both. Uncontrolled microbial contamination can affect fuel specification properties adversely. As discussed in Guide D 6469, microbes can cause a variety of operational problems, including filter plugging and microbially influenced corrosion (MIC), the latter of which causes valve failure, tank and pipeline failure.

These practices for microbiological sampling decrease the risk of contaminating samples with extraneous microbes, thereby increasing the probability that the original microbial population in the sample does not change significantly between the time of sampling and the time of testing.

The objective of sampling for microbiological testing is to obtain a representative sample that is likely to reflect the degree and nature of microbial contamination in the system from which the sample is collected. Manual 47 addresses the rational for and design of microbial contamination programs.

The physical, chemical and microbiological property tests to be performed on a sample will dictate the sampling procedures, the sample quantity required, and many of the sample handling requirements.

Fuel systems are not normally designed to facilitate optimal microbiological sampling. Consequently, the selection of sampling device and sample source reflect compromises between accessibility and suitability for meeting the sample collection objective.

The guidance provided in Practice D 4057 generally applies to this practice as well. Consequently, this practice will address only those procedures that apply uniquely to microbiological sampling.

1.1 This practice covers aspects of sample device preparation and sample handling that prevent samples from becoming contaminated with microorganisms not originally contained within the sample.

1.2 This practice also covers sample handling considerations that reflect the perishability of samples collected for microbiological testing.

1.3 This practice supplements Practice D 4057 by providing guidance specific to the manual sampling of fuels when samples are to be tested for microbial contamination.

1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.