Question: I need to place a Globally Harmonized System (GHS) classification on absorbents that we use to absorb flammable liquids, but I’m not sure how to classify the material. Would it be considered liquid or solid?
Answer: In the old Hazard Communication Standard (HCS), an absorbent soaked with a flammable liquid would most likely have been considered a flammable solid under the test method described in 16 CFR 1500.44 if it had a self-sustained flame rate greater than 1/10” along its major axis.
But, the new GHS criterion eliminated the reference to 16 CFR 1500.44. If you look at the definition/criteria for flammable solids from 29 CFR 1910.1200 Appendix B, nothing describes an absorbent mat containing a flammable liquid:
B.7 FLAMMABLE SOLIDS
B.7.1 DEFINITIONS Flammable solid means a solid which is a readily combustible solid, or which may cause or contribute to fire through friction. Readily combustible solids are powdered, granular, or pasty chemicals which are dangerous if they can be easily ignited by brief contact with an ignition source, such as a burning match, and if the flame spreads rapidly.
B.7.1 DEFINITIONS Flammable solid means a solid which is a readily combustible solid, or which may cause or contribute to fire through friction. Readily combustible solids are powdered, granular, or pasty chemicals which are dangerous if they can be easily ignited by brief contact with an ignition source, such as a burning match, and if the flame spreads rapidly.
B.7.2 CLASSIFICATION CRITERIA
B.7.2.1 Powdered, granular or pasty chemicals shall be classified as flammable solids when the time of burning of one or more of the test runs, performed in accordance with the test method described in the UN ST/SG/AC.10 (incorporated by reference; See §1910.6), Part III, sub-section 33.2.1, is less than 45 s or the rate of burning is more than 2.2 mm/s (0.0866 in/s).
B.7.2.2 Powders of metals or metal alloys shall be classified as flammable solids when they can be ignited and the reaction spreads over the whole length of the sample in 10 min or less.
B.7.2.3 Solids which may cause fire through friction shall be classified in this class by analogy with existing entries (e.g., matches) until definitive criteria are established.
B.7.2.4 A flammable solid shall be classified in one of the two categories for this class using Method N.1 as described in Part III, sub-section 33.2.1 of the UN ST/SG/AC.10 (incorporated by reference; See §1910.6), in accordance with Table B.7.1”
So, if it’s not a flammable solid, what is it? It falls under the catch-all category known as Hazard Not Otherwise Classified (HNOC), which the Occupational Safety and Health Administration (OSHA) defines as an item that has “an adverse physical or health effect identified through evaluation of scientific evidence during the classification process that does not meet the specified criteria for the physical and health hazard classes addressed in this section. This does not extend coverage to adverse physical and health effects for which there is a hazard class addressed in this section, but the effect either falls below the cut-off value/concentration limit of the hazard class or is under a GHS hazard category that has not been adopted by OSHA (e.g., acute toxicity Category 5)” [29 CFR 1910.1200(c)].
OSHA provides come clarification on the HazCom FAQ page:
Q: How has OSHA addressed hazards covered under the current Hazard Communication Standard that have not been addressed by the GHS?
A: In the Notice of Proposed Rulemaking (NPRM), OSHA proposed to include hazards currently covered under the Hazard Communication Standard (HCS) that have yet to be addressed by the GHS (OSHA provided several examples: simple asphyxiants and combustible dust) in a separate category called “Unclassified Hazards.” In response to comments from the regulated community, OSHA has renamed the category to “Hazards Not Otherwise Classified (HNOC)” to minimize confusion. In the final HCS, HNOC hazards will not be required to be disclosed on the label but will be required to be disclosed in section 2 of the Safety Data Sheet (SDS). This reflects how GHS recommends these hazards should be disclosed. Chemical manufacturers and importers are expected to assess these hazards when they are conducting their hazard evaluation of physical and health hazards. A new or separate evaluation is not required. Also in the final standard, in response to comments, OSHA has removed pyrophoric gases, simple asphyxiants and combustible dust from the HNOC hazard category and has addressed these chemicals individually.
There are also interpretation letters on classifying something as HNOC and labeling HNOC hazards.
I can tell you what we know about our absorbents that might be relevant: They take on the properties of the chemicals they have absorbed. Flammable vapors in the absorbent could still ignite if there is an ignition source, much in the same way that they could ignite if you had an open container of a flammable liquid sitting somewhere in the facility and exposed the vapors to an ignition source.
In the event of a fire, polypropylene absorbents won’t support combustion, meaning they won’t make a fire worse or do anything to sustain a fire. When a flame is removed from the absorbent, it will self-extinguish. In the event of a fire, the absorbent will melt and turn into a little plastic puddle. This happens at about 250 degrees Fahrenheit. When it cools, it will harden into a crisp sheet of plastic that breaks or crumbles easily.
You should also look at the Safety Data Sheet (SDS) for the absorbents you need to classify to in their virgin state, which will provide additional physical properties that you might need to know to make a determination.
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