Petroleum liquids with a flash point are primarily classified into two main categories: Flammable Liquids and Combustible Liquids. This classification is based on their flash point, which is the lowest temperature at which a liquid gives off enough vapor to form an ignitable mixture with air near its surface. Here's a breakdown of the classifications, commonly defined by organizations like NFPA (National Fire Protection Associatio) and OSHA (Occupational Safety and Health Administration):
NFPA (National Fire Protection Association)
Flammable Liquids (Class I Liquids) - These are liquids that have a flashpoint below 100°F (37.8°C). They pose a higher fire hazard because they can ignite easily at normal working temperatures. Flammable liquids are further divided into categories:
- Class IA - Flash point below 73°F (22.8°C) and a boiling point below 100°F (37.8°C).
- Class IB - Flash point below 73°F (22.8°C) and a boiling point at or above 100°F (37.8°C).
- Class IC - Flash point at or above 73°F (22.8°C) and below 100°F (37.8°C).
Combustible Liquids (Class II and Class III Liquids) - These are liquids that have a flash point at or above 100°F (37.8°C). They generally require a higher temperature to ignite compared to flammable liquids. Combustible liquids are divided into:
- Class II Combustible Liquids - Flash point at or above 100°F (37.8°C) and below 140°F (60°C).
- Class III Combustible Liquids - Flash point at or above 140°F (60°C).
- Class IIIA - Flash point at or above 140°F (60°C) and below 200°F (93°C).
- Class IIIB - Flash point at or above 200°F (93°C).
Non-Combustible Liquids - Liquids with a flash point above 200°F (93.3°C) or those that do not sustain combustion. These are generally considered low fire risk, such as heavy lubricating oils.
OSHA (Occupational Safety and Health Administration)
- Category 1 - Flash point below 73.4°F (23°C) and a boiling point at or below 95
- Category 2 - Flash point below 73.4°F (23°C)
- Category 3 - Flash point at or above 73.4°F (23°C) and a flash point at or below 140°F (60°C). This category includes liquids that were previously often classified as "combustible" under older systems.
- Category 4 - Flash point above 140°F (60°C) and a flash point at or below 199.4°F (93°C). These liquids have higher flash points, making them less prone to ignition at typical room temperatures, but they still pose a fire hazard, especially when heated.
