Section 1090.1337 - Demonstrating homogeneity(a) Certification test results corresponding to manual sampling as specified in § 1090.1335(b) are valid only if collected samples meet the homogeneity specifications in this section, except that the homogeneity testing requirement does not apply in the following cases:(1) There is only a single sample using the procedure specified in § 1090.1335(b)(2) .(2) Upright cylindrical tanks that have a liquid depth of less than 10 feet.(3) You draw spot or tap samples as specified in paragraph (c) of this section, test each sample for every parameter subject to a testing requirement, and use the worst-case test result for each parameter for purposes of reporting, meeting per-gallon and average standards, and all other aspects of compliance.(4) Sampling at a downstream location where it is not possible to collect separate samples and steps are taken to ensure that the batch is well mixed.(b)(1) Testing performed to establish homogeneity is not considered certification testing, except as specified in paragraph (b)(2) of this section.(2) Homogeneity testing may be used as certification testing if any of the following criteria are met: (i) All tested samples meet all applicable per-gallon standards.(ii) The testing meets the requirement in § 1090.1335(b)(2)(ii) .(iii) The testing follows the procedures specified in paragraph (a)(3) of this section.(c) Use spot sampling as specified in § 1090.1335(b)(2) for homogeneity testing. Tap sampling is acceptable if spot sampling is impractical for a given facility.(d) Demonstrate homogeneity for gasoline using two of the procedures specified in this paragraph (d) with each sample. For summer gasoline, the homogeneity demonstration must include RVP measurement.(1) Measure API gravity using ASTM D287, ASTM D1298, ASTM D4052, or ASTM D7777 (incorporated by reference in § 1090.95 ).(2) Measure the sulfur content as specified in § 1090.1360 .(3) Measure the benzene content as specified § 1090.1360 .(4) Measure the RVP as specified in § 1090.1360 .(e) For testing to meet the diesel fuel standards in subpart D of this part, demonstrate homogeneity using one of the procedures specified in paragraph (d)(1) or (2) of this section.(f) Consider the batch to be homogeneous for a given parameter if the measured values for all tested samples vary by less than the published reproducibility of the test method multiplied by 0.75 (R * 0.75). If reproducibility is a function of measured values, calculate reproducibility using the average value of the measured parameter representing all tested samples. Calculate using all meaningful significant figures as specified for the test method, even if § 1090.1350(c) describes a different precision. For cases that do not require a homogeneity demonstration under paragraph (a) of this section, the lack of homogeneity demonstration does not prevent a quantity of fuel, fuel additive, or regulated blendstock from being considered a batch for demonstrating compliance with the requirements of this part.