1.1 A condition during flash point testing can occur with certain mixtures whereby the nonflammable component of the sample tends to inert the vapor space above the liquid, thus preventing a flash. Under this condition, the flash point of the material is masked resulting in the reporting of incorrect high flash point or no flash point.
1.2 This flash point masking phenomenon most frequently occurs with ignitable liquids that contain certain halogenated hydrocarbons such as dichloromethane (methylene chloride) and trichloroethylene.
1.3 Under this condition, no distinct flash as defined in 3.1.1 is observed. Instead a significant enlargement of the test flame and a change in the color of the test flame from blue to yellow-orange laminar flame is observed.
1.4 Under this condition, continued heating and testing for flash point at temperatures above ambient temperature, have resulted in significant burning of the ignitable vapor outside the test cup, often above the test flame. This can be a potential fire hazard if not recognized.
1.5 It is recommended that if this condition is encountered during the flash point testing of these type of materials, testing should be discontinued.
1.6 Further commentaries regarding flash point test and flammability of mixtures can be found in Test Method E 502.
