GENERAL
The lowest temperature corrected to a barometric pressure of 101.3 kPa (760 mm Hg), at which application of a test flame causes the vapor of a sample to ignite under specified test conditions. The sample is deemed to have flashed when a large flame appears and instantaneously propagates itself over the surface of the sample. Occasional appearance of a blue halo or an enlarged flame, close to the actual flash point is not considered a true flash point.
Flash point measures the tendency of a sample to form a flammable mixture with air under controlled laboratory conditions. Flash point data are used in shipping and safety regulations to define "flammable" and "combustible" materials. Flash point data can also indicate the possible presence of highly volatile and flammable material in a relatively nonvolatile or nonflammable material.
Erroneously high flash points can be obtained when precautions are not taken to avoid the loss of volatile material. Samples should not be stored in plastic bottles, since the volatile material may diffuse through the walls of the container. The containers should not be opened unnecessarily. The samples should not be transferred between containers unless the sample temperature is at least 20° F (11° C) below the expected flash point.
Flash point should not be confused with autoignition temperature (ASTM Test Method E 659), which measures spontaneous combustion with no external source of ignition.
There are five different methods of determining flash point:
