ASTM D7978 : 24

1.1 This test method covers a procedure that can be used in the field or in a laboratory to quantify culturable, viable aerobic microorganisms present as contaminants in liquid fuels, including those blended with synthesized hydrocarbons or biofuels, with kinematic viscosities (at 40 °C) of ≤24 mm² s^-1 and heavy and residual fuels with kinematic viscosities (at 40 °C) of ≤700 mm² s^-1 and in fuel-associated water.

1.2 This test method quantitatively assesses culturable, viable aerobic microbial content present in the form of bacteria, fungi, and fungal spores. Results are expressed as the total number of microbial colony forming units (CFU)/L of fuel or total number of CFU/mL of associated water. The number of CFU should not be interpreted as absolute values but should be used as part of a diagnostic or condition monitoring effort; for example, these values can be used to assess contamination as absent, light, moderate, or heavy.

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

1.4 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.