According to 49 CFR 173.120 [Title 49 – Transportation; Subtitle B -- Other Regulations Relating to Transportation; Chapter I -- Pipeline and Hazardous Materials Safety Administration, Department of Transportation; Subchapter C -- Hazardous Materials Regulations; Part 173 -- Shippers -- General Requirements for Shipments and Packagings; Subpart D -- Definitions Classification, Packing Group Assignments and Exceptions for Hazardous Materials Other Than Class 1 and Class 7], flash point means “the minimum temperature at which a liquid gives off vapor within a test vessel in sufficient concentration to form an ignitable mixture with air near the surface of the liquid. It shall be determined as follows:
(i) For a homogeneous, single-phase, liquid having a viscosity less than 45 S.U.S. at 38 [degrees]C (100 [degrees]F) that does not form a surface film while under test, one of the following test procedures shall be used:
(A) Standard Method of Test for Flash Point by Tag Closed Tester, (ASTM D 56);
(B) Standard Methods of Test for Flash Point of Liquids by Setaflash Closed Tester, (ASTM D 3278); or
(C) Standard Test Methods for Flash Point by Small Scale Closed Tester, (ASTM D 3828).
(ii) For a liquid other than one meeting all of the criteria of paragraph (c)(1)(i) of this section, one of the following test procedures shall be used:
(A) Standard Method of Test for Flash Point by Pensky -- Martens Closed Tester, (ASTM D 93). For cutback asphalt, use Method B of ASTM D 93 or alternate tests authorized in this standard; or
(B) Standard Methods of Test for Flash Point of Liquids by Setaflash Closed Tester (ASTM D 3278).”