Flammable Liquids and Class 3

Abstract

According to regulatory definitions, flammable liquids and combustible liq uids are those which can undergo combustion under conditions incident to transportation. A flammable liquid preparation is any liquid mixture or compound readied for some kind of use, possibly medicinal, that remains flammable. A material’s tendency to be flammable is characterized using the following factors:

• Flash point: the lowest temperature at which vapours above a liquid will ignite when exposed to an ignition source. For example, the flash point of a No.1 fuel oil is 54°C (open cup) and 59°C (closed cup). Materials transported above their flash points present a significant risk of fire if they come into contact with electrical equipment, electrostatic sparks, automotive ignition systems, open flames, and other ignition systems.

• Fire point: the lowest temperature at which the vapours evolve above a liquid at a sufficient rate to support ongoing combustion; e.g., the same No.1 fuel oil cited above may have a fire point of 63°C.

• The presence of other substances in the liquid; e.g., high concentrations of a nonflammable material will reduce the liquid’s ability to sustain combustion.

• The presence of water if the material is water-miscible; the dissolution of a miscible flammable liquid in water affects the flammability. For example, pure ethanol will flash at 12.7°C; a 70% mixture by weight in water will flash at 23°C; and a 24% mixture in water at 60.5°C.

• Transportation temperature: materials with high flash points may be considered flammable if transported at temperatures above their flash points.