Flammable vs Combustible: Understanding Hazardous Material Classification

What criteria does the USCG use to classify cargoes as flammable or combustible? The USCG classifies cargoes as either flammable or combustible based on flash point and further divides flammable liquids based on Reid Vapor Pressure.

USCG Hazardous Material Classification

The United States Coast Guard (USCG), in accordance with the United States Department of Transportation hazardous materials regulations, classifies liquids based on their flash point to determine if they are flammable or combustible.

For liquids with a flash point below 60 °C, the USCG classifies them as flammable. This includes substances such as used solvents and waste oils, which are often categorized as hazardous waste under EPA regulations. Additionally, materials like ignitable compressed gases and oxidizers are also classified as flammable.

The flash point is defined as the lowest temperature at which a liquid can form an ignitable mixture in air near its surface. It serves as a key indicator to distinguish between flammable and combustible liquids.

Furthermore, the USCG utilizes the Reid Vapor Pressure to further classify flammable liquids. This measurement determines the volatility of a liquid and helps assess the risk of flammability and explosiveness, particularly for petroleum products.

Cargo handlers, including personnel in the US Navy like Aviation Boatswain's Mates, rely on these classifications to identify and manage hazardous materials such as JP-5 fuel, as shown in Figure 1.12.2.

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