Chemicals

But It Wasn’t Flammable Before! GHS Changed the Meaning of ‘Flammable Liquids’

A chemical that meets the definition of “flammable” requires special precautions in handling, use, transfer, and storage. But the Occupational Safety and Health Administration (OSHA) has changed the definition of “flammable” throughout its general industry and construction standards to align them with the Globally Harmonized System of Classification and Labelling of Chemicals (GHS).

Most employers are by now aware of the changes to OSHA’s hazard communication standard (HCS) that resulted when the HCS was aligned with GHS. But other standards regulating hazardous chemicals were also revised to align with GHS. Changes to the definitions of flammable and liquids affected not only the HCS but also OSHA’s Flammable and Combustible Liquids standard, 29 CFR 1910.106—which is now simply titled Flammable Liquids.

Old vs. New

Before it was aligned with GHS, 29 CFR 1910.106 gave these definitions for flammable and combustible liquids:

  • A flammable liquid was defined as “Any liquid having a flash point below 100°F (37.8°C)”
  • A combustible liquid was defined as “Any liquid with a flashpoint at or above 100°F (37.8°C), but below 200°F (93.3°C)”

Flammable and combustible liquids were further subdivided into classes:

  • All flammable liquids were Class I liquids.
    • Class IA liquids had flash points below 73°F (22.8°C) and boiling points below 100°F (37.8°C).
    • Class IB liquids had flash points below 73°F (22.8°C) and boiling points above 100°F (37.8°C).
    • Class IC liquids had flash points at or above 73°F (22.8°C) and below 100°F (37.8°C)
  • Combustible liquids were Class II or III liquids.
    • Class II liquids had flash points at or above 100°F (37.8°C) and below 140°F (60°C).
    • Class IIIA liquids had flash points at or above 140°F (60°C)  and below 200°F (93.3°C)
    • Class IIIB liquids had flash points at or above 200°F (93.3°C). When these chemicals were heated within 30°F (16.7°C) of their flash points, they were treated as Class IIA liquids.


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Under GHS, all liquids with a flash point of not more than 199.4°F (93°C) are categorized as flammableliquids. Flammable liquids are further subdivided into categories:

  • Category 1 liquids have flash points below 73.4°F (23°C) and boiling points at or below 95°F (35°C).
  • Category 2 liquids have flashpoints below 73.4°F (23°C) and boiling points above 95°F (35°C).
  • Category 3 liquids have flashpoints at or above 73.4°F (23°C) and at or below 140°F (60°C). When Category 3 liquids with flash points at or above 100°F (37.8°C) are heated for use to within 30°F (16.7°C) of their flash point, they must be handled in accordance with the requirements for a Category 3 liquid with a flashpoint below 100°F (37.8°C).
  • Category 4 liquids have flash points above 140°F (60°C) and at or below 199.4°F (93°C). When Category 4 flammable liquids are heated for use to within 30°F (16.7°C) of their flash points, they must be handled in accordance with the requirements for a Category 3 liquid with a flashpoint at or above 100°F (37.8°C).
  • In addition, the new rules specify that when a liquid with a flash point greater than 199.4°F (93°C) is heated for use to within 30°F (16.7°C) of its flash point, it must be handled in accordance with the requirements for a Category 4 flammable liquid.

See the table for an approximate comparison of the classes and categories. Note that GHS primarily uses the metric system as its standard of measurement (although it retains 100°F as a cutoff point), so the cutoff temperatures do not match up exactly between the two systems. The numbers below are taken from the GHS.

 

<73.4°F
(23°C)

<100°F
(37.8°C)

<140°F
(60°C)

<199.4°F
(93°C)

>199.4°F
(93°C)

Old 1910.106

Flammable

Combustible

 

Classes

IA, IB

IC

II

IIIA

IIIB

New
GHS

Flammable

 

      Categories

1,2

3

4

 


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Do the Storage Requirements Change?

As you can see, OSHA now calls all liquids with a flash point below 199.4°F (93°C) “flammable liquids.” The term “combustible liquids” is no longer used. The good news is that the storage requirements found in 1910.106 have not, in fact, changed.  

The main effect of the change to the standards is to make the wording slightly more cumbersome. “Category 3” under GHS encompasses what OSHA previously called “Class IC” and also “Class II,” taking in flammable and combustible liquids with flash points up to 140°F—but the break point for many storage requirements is 100°F. So the standard now has different requirements for “Category 3 flammable liquids with a flashpoint below 100°F (37.8°C),” (flammable liquids that were formerly Class IC) and “Category 3 flammable liquids with a flashpoint at or above 100°F (37.8°C),” (formerly Class II combustible liquids)—but they are the same standards as before, just reworded for consistency with GHS hazard categories.

Tomorrow, we’ll look at some of the specifics of flammable chemical storage.