Flammable and combustible liquids expose people to fire hazards, and for this reason, the Occupational Safety and Health Administration (OSHA) requires special precautions for their handling, storage, transportation and use.
When OSHA adopted the Globally Harmonized System for Classifying and Labeling of Chemicals (GHS), it resulted in changes to the OSHA’s hazard communication standard (HCS). However, the GHS alignment also required the revision of other standards related to the regulation of hazardous chemicals, including the definition of flammable and combustible liquids and OSHA’s Flammable and Combustible Liquids Standard, 29 CFR 1910.106. The standard is now titled ‘Flammable Liquids’.
Old Flammable and Combustible Definition and Classification
Before the implementation of GHS, liquids were classified as being either “Flammable” or “Combustible” under OSHA’s standard.
‘Flammable liquid’ was defined as “any liquid having a flash point below 37.8°C. Meanwhile, ‘combustible liquid’ was defined as “any liquid having a flash point at or above 37.8°C, but below 93.3°C.
They were further subdivided into these classes:
- Flammable Liquids – Class I liquids:
- Class IA Liquids – flash points below 22.8°C and boiling points below 37.8°C.
- Class IB Liquids – flash points below 22.8°C and boiling points below 37.8°C.
- Class IC Liquids – flash points at or above 22.8°C and below 37.8°C.
- Combustible Liquids – Class II or Class III Liquids:
- Class II Liquids – flash points at or above 37.8°C and below 60°C.
- Class IIIA Liquids – flash points at or above 60°C and below 93.3°C.
- Class IIIB Liquids – flash points at or above 93.3°C. When heated within 16.7°C of their flash points, these chemicals are treated as
Class IIA Liquids.
New Flammable Classification
After adopting the GHS, OSHA now classifies all liquids with a flash point of no more than 93°C as flammable liquids and are divided into four categories:
- Category 1 Liquids- flash points below 23°C and boiling points at or below 35°C.
- Category 2 Liquids – flash points below 23°C and boiling points above 35°C.
- Category 3 Liquids – flash points at or above 23°C and at or below 60°C. When Category 3 Liquids with flash points at or above 37.8°C are heated within 16.7°C of their flash point, they must be handled according to the requirements for a Category 3 Liquid with a flash point below 37.8°C.
- Category 4 Liquids – flash points above 60°C and at or below 93°C. When Category 4 Liquids are heated to within 16.7°C of their flash
point, they must be handled according to the requirements for a Category 4 Liquid with a flash point at or above 37.8°C.
Furthermore, the new regulations stipulate that when flammable liquids with a flash point greater than 93°C are heated to within 16.7°C of their flash point, these chemicals must be handled according to the requirements for a Category 4 Liquid.
The main difference between the old and new classifications is that all liquids with a flash point below 93°C are now ‘flammable liquids’, eliminating the
‘combustible liquid’ classification. The storage requirements found in 29 CFR 1910.106 have not changed.