The significant digit differences between the RVP standard and the enforcement tolerance arise from EPA's desire to resolve any questions about rounding of RVP measurements when an enforcement tolerance has been applied.

Accordingly, for example, the 0.30 psi RVP enforcement tolerance would preclude rounding of the second significant digit of the Rvp standard.(7/1/94)

This question and answer was posted at Consolidated List of Reformulated Gasoline and Anti-Dumping Questions and Answers: July 1, 1994 through November 10, 1997 (PDF)(333 pp, 18.17 MB, EPA420-R-03-009, July 2003, About PDF)