Editing Flash point (section)

== Measurement ==
There are two basic types of flash point measurement: '''open cup''' and '''closed cup'''.<ref>Jansen and Hyams.pp62</ref> In open cup devices, the sample is contained in an open cup which is heated and, at intervals, a flame brought over the surface. The measured flash point will actually vary with the height of the flame above the liquid surface and, at sufficient height, the measured flash point temperature will coincide with the [[fire point]]. The best-known example is the [[Cleveland open cup method|Cleveland open cup]] (COC).<ref>[https://www.astm.org/Standards/D92.htm "Standard Test Method for Flash and Fire Points by Cleveland Open Cup Tester"], ASTM.org</ref>

There are two types of closed cup testers: non-equilibrial, such as Pensky-Martens, where the vapours above the liquid are not in temperature equilibrium with the liquid, and equilibrial, such as Small Scale (commonly known as Setaflash), where the vapours are deemed to be in temperature equilibrium with the liquid. In both these types, the cups are sealed with a lid through which the ignition source can be introduced. Closed cup testers normally give lower values for the flash point than open cup (typically {{convert|5|-|10|C-change|0|disp=or}} lower) and are a better approximation to the temperature at which the vapour pressure reaches the [[lower flammable limit]].  In addition to the Penskey-Martens flash point testers, other non-equilibrial testers include TAG and Abel, both of which are capable of cooling the sample below ambient for low flash point materials.  The TAG flash point tester adheres to ASTM D56 and has no stirrer, while the Abel flash point testers adheres to IP 170 and ISO 13736 and has a stirring motor so the sample is stirred during testing.

The flash point is an empirical measurement rather than a fundamental physical parameter. The measured value will vary with equipment and test protocol variations, including temperature ramp rate (in automated testers), time allowed for the sample to equilibrate, sample volume and whether the sample is stirred.

Methods for determining the flash point of a liquid are specified in many standards. For example, testing by the [[Pensky-Martens closed cup]] method is detailed in [[ASTM]] D93, IP34, ISO 2719, DIN 51758, JIS K2265 and AFNOR M07-019. Determination of flash point by the Small Scale closed cup method is detailed in ASTM D3828 and D3278, EN ISO 3679 and 3680, and IP 523 and 524.

CEN/TR 15138 Guide to Flash Point Testing and ISO TR 29662 Guidance for Flash Point Testing cover the key aspects of flash point testing.