Flash point is one important indicator of the relative flammability hazard of solvents and solvent-containing products; therefore, this is a very important specification for solvents and paints. The flash point of a liquid may be defined as the lowest temperature at which the liquid, in contact with air, is ignited by a spark or flame under specified conditions. The Abel method (Institute of Petroleum Test Method 170), the Pensky-Martens closed-cup method (ASTM D 93), the Tag open-cup method (ASTM D 1310), the Tag closed-cup method (ASTM D 56), the Setaflash closed-cup method (ASTM D 3278), and ISO 3679 and ISO 3680 are some of the test methods used to determine flash point of a system; each method requires specific protocols and equipment. For compliance with regulations related to transportation and storage, the flash point must be determined by a specified method.
Flash point is roughly inversely proportional to volatility. When there are mixtures of miscible solvents, which is true for most coatings, in most cases the flash point can be assumed to be that of the solvent with the lowest flash point, provided that a substantial proportion of that component is present, such as 5 % or more.