V. Flammability of Vapor-Air Mixtures
The flammability of a hydrocarbon vapor-air mixture depends on its vapor pressure, flash point and temperature. These properties are used to classify petroleum products whose electrical resistivities are high enough to enable them to accumulate significant electrostatic charges under certain handling conditions. Following are the three petroleum product Vapor Pressure Classifications, including common examples:
Low – Those with a closed cup flash point above 100°F (38°C).
These products do not develop flammable vapors under normal handling conditions. However, conditions for ignition may exist, if handled at temperatures above their flash points, are contaminated with higher vapor-pressure materials, or are transferred into containers where vapors are at concentrations at or above those necessary to produce a flammable mixture.
Examples: #2 Fuel Oil; Kerosene, Diesel, Jet Fuel A (commercial), Motor Oil, Asphalt, and Safety Solvents Intermediate – Those with a closed-cup flash point below 100°F (38°C).
Intermediate – Those with a closed-cup flash point below 100°F (38°C).
These products may create a flammable mixture in the vapor space at ambient temperatures.
Examples: Xylene, Benzene, Toluene, Jet B (commercial), JP-4 (military), and Stoddard Solvents
High – Those with a Reid Vapor pressure above 4.5 psi absolute (31 kilopascals).
These products, under normal handling temperatures in a closed vapor space, will rapidly produce a mixture too rich to be flammable. However, in some areas, a vapor space may pass through the flammable range before becoming too rich.
Examples: Motor and Aviation Gasoline’s (sic), and high vapor pressure Naphtha’s (sic)