Flashpoint temperature, defined

Flashpoint — the lowest temperature of a liquid at whieh it gives off enough vapor to form an ignitable mixture with air near the surfaee of the liquid within the vessel used. Two tests are used—Open Cup and Closed Cup. Generally, the Open Cup method results in flashpoints 5° to 10° higher than the Closed Cup method. Flashpoint < 140°F (Closed Cup) is the eriterion used by EPA to deeide whether a ehemieal is hazardous by ignitability. DOT defines materials with flashpoints of < 100°F as flammable materials, and between 100° and 200°F as eombustible. 

Flammability, the tendency of a material to bum, can only be subjectively defined. Many materials that we normally do not consider flammable will bum, given high enough temperatures. Neither can flammability be gauged by the heat content of materials. Fuel oil has a higher heat content than many materials considered more flammable because of their lower flashpoint. In fact, flashpoint has become the... 

Flashpoint is the temperature at which an inflammable liquid builds enough vapour so that this, together with air, forms an inflammable mixture in the presence of an igniting flame.The inflammation has to be very brief when this parameter is measured. If the combustion lasts for longer than five seconds, this temperature is defined as fire point. Fire point is never used because it is really difficult to obtain an accurate value. Flashpoint is the most important parameter in fire hazard. It plays an essential role in the determination of risk criteria related to the inflammability of a substance. 

In the same way flashpoint oc can be defined as the temperature to which one has to heat a liquid so that Its vapour gives an equilibrium concentration equal to Its stoichiometric concentration. 

To form a flammable vapor-air mixture above the surface of a liquid, the temperature of the liquid must be sufficiently high, and the lowest temperature at which a flammable gas-air mixture is formed at one atmosphere is defined as the flashpoint. ... 

Flammable hquids are divided into various classes, as given in Table 3.4. The definitions depend upon the flashpoints and in some cases the boiling points of the liquids. The flashpoint of a liquid is l aUy defined in terms of specific test procedures used to determine it, but conceptually it is the minimum temperature at which a hquid forms a vapor above its surface in sufficient concentration that it may be ignited. In Table 3.4, the first temperature is in degrees Celsius and the temperature in parentheses () is the equivalent Fahrenheit temperature. 

Most flammable liquids only form an explosive mixture between certain concentration limits. Above and below this level of concentration the mix will not explode. The lowest temperature at which sufficient vapour is given off from a flammable substance to form an explosive gas-air mixture is called the flashpoint. A liquid which is safe at normal temperatures will require special consideration if heated to flashpoint. An area in which an explosive gas-air mixture is present is called a hazardous area, as defined by the British Standards, and any electrical apparatus or equipment within a hazardous area must be classified as flameproof. 

---