NFPA/ICC versus GHS Flammable and Combustible Liquid Categories

For decades, all flammable and combustible liquids have been categorized via the NFPA liquid classification. This was copied by the International Building Code (IBC) and International Fire Code (IFC) as well as most other US codes. The release of the new Globally Harmonized System of Classification and Labelling of Chemicals (GHS) which was recently adopted by OSHA has created some confusion.

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Here is a comparison of the two systems:

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As you can see, the differences appear minor.

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All NFPA and IBC/IFC codes reference specific requirements against the NFPA definitions.? Neither has indicated any impending intent to change in the near future. NFPA Class IIIA and IIB liquids are the same as GHS Category 4 and 5 liquids except for? 1 F (199 F vs. 200 F). This small difference is unlikely to often be a problem or concern. While the difference between NFPA Class IA and IB liquids and GHS Category 1 and 2 liquids is larger, 5 F, this is probably also not a major issue except in some rare cases.

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The combining of NFPA Class IC and II liquids into GHS Category 3 liquids is more problematic. Currently all US codes consider only NFPA Class I liquids as flammable. Class II liquids are combustible. As a result, considering GHS Category 3 liquids as flammable adds a significant number of chemicals into a category which, in the US, requires more stringent requirements and lowers the maximum allowable quantity (MAQ) in many areas. Many larger companies, primarily oil, gas, and chemicals, often voluntarily extended their internal definition of flammable above the 100 F NFPA level into some part of the Class II range. This extension was justified fortwo reasons. First, the common code guidance, repeated in the GHS system, that liquids heated to within 10 - 30 F (different codes recommended different values at different times) of their flash point should be considered as the next most hazardous classification. So many organizations voluntarily extended the flammable definition anywhere from 110 to 130 F. Second, solar gain from the sun can be 5-25 F ,again suggesting some extension of the 100 F maximum is warranted for exterior installations or storage. Many other organizations stayed with the strict interpretation and considered 100 F as the dividing line.

?OSHA has had, for years, two different definitions for flammable liquids.

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?(See https://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=INTERPRETATIONS&p_id=27488? for more information.) So, some dichotomy is normal although not desirable.

?What does this difference mean for research?

?Sadly, it means one needs to identify the correct category for the intended use. Most building and fire codes, as well as all NFPA standards, will continue to use the NFPA liquid classification for the foreseeable future. For pure compounds and common mixtures finding the flash point and boiling point is usually not an issue, however irksome. For specialty mixtures or unique or novel liquids, it can be more challenging. In that case researchers may need to either arrange fore testing to determine the flash point, estimate the flash point by comparison with similar (enough) compounds, or be conservative and assume the liquid is the a higher hazard (lower classification). Testing can be expensive and time consuming particularly if the organization must contract out the test. Estimating the flash point by comparison is sometimes difficult and always fraught with the potential for error, raising the potential for a higher hazard then anticipated. Assuming a lower classification (and so higher hazard) may be acceptable for small quantities infrequently used but usually creates a problem with larger quantities. It is not uncommon for a research organization to make a conservative assumption for some initial work to establish viability and then arrange for testing if the work will expand or continue.