Construction Concerns: Classification of Flammable and Combustible Liquids

10/26/15

By Gregory Havel
Fire Engineering

Since the inception of the U.S. Department of Transportation (DOT) regulations regarding hazardous materials-including combustible and flammable liquids-the categories “flammable” and “combustible” have not matched the boundaries of similar classifications in National Fire Protection Association (NFPA) 704, System for the Identification of the Hazards of Materials for Emergency Response, 2012 edition, and other NFPA standards with which most emergency responders are already familiar.

According to the NFPA standards, a flammable liquid is any liquid with a flash point below 100°F (37.8°C):

  • Class IC liquids have a flash point below 100°F (37.8°C).
  • Class IB liquids have a flash point below 73°F (22.8°C) and a boiling point at or above 100°F (37.8°C).
  • Class IA liquids have a flash point below 73°F (22.8°C) and a boiling point below 100°F (37.8°C).

According to the U.S. DOT regulations, a flammable liquid is any liquid with a flash point below 140°F (60°C), which includes NFPA Class I flammable liquids and Class II combustible liquids. U.S. DOT flammable liquids must be labeled and placarded for transport with red flammable liquid placards.

According to the U.S. DOT regulations, a combustible liquid is any liquid with a flash point at or above 140°F (60°C), which includes NFPA Class IIIA and IIIB combustible liquids. These must be labeled and placarded for transport with red combustible liquid placards.

The upper sections of Figure 1 (click to enlarge as a PDF) show the relationship between the categories of “flammable” and “combustible” liquids in NFPA 704 and other NFPA codes and standards and the U.S. DOT regulations. These are based on the flash point of the liquid, except for the boundary between NFPA Class IA and IB, as described above.

Flammable Photo1

The middle section of Figure 1 shows the relationship of the hazard categories established in NFPA 704, with the classifications as flammable and combustible liquids. Note that in this system, “0” is not considered ignitable, while “4” is considered extremely flammable.

A few years ago, the U.S. Occupational Safety and Health Administration (OSHA) adopted the United Nations’ “Globally Harmonized System” (GHS) of product labeling and safety data sheets (SDSs), which are similar to the material SDSs required by the U.S. DOT. This is the new system for use in places of employment, including construction job sites, and is presently in a transition between the old OSHA regulations (which match the current U.S. DOT regulations) and the United Nations’ GHS, and which must be fully implemented by employers, chemical manufacturers, importers, and distributors by the end of 2015.

The bottom section of Figure 1 shows the relationship of the hazard categories under the GHS with the NFPA and U.S. DOT classifications. Under the GHS:

  • Category 1 is approximately the equivalent by flash point and boiling point to NFPA Class IA. On the SDS, it will include the signal word “DANGER” and a flammable pictogram (Figure 2) in addition to any other pictograms required by its other properties.
  • Category 2 is approximately equivalent by flash point and boiling point to NFPA Class IB. On the SDS, it will include the signal word “DANGER” and a flammable pictogram (Figure 2) in addition to any other pictograms required by its other properties.
  • Category 3 is approximately equivalent by flash point to NFPA Class IC flammable liquids and Class II combustible liquids. On the SDS, it will include the signal word “WARNING” and either a flammable pictogram (Figure 2) or a general warning pictogram (Figure 3) in addition to any other pictograms required by its other properties.
  • Category 4 is approximately equivalent by flash point to NFPA Class IIIA combustible liquids. On the SDS, it will include no signal word (unless required by its other properties) and may have either a flammable pictogram (Figure 2) or a general warning pictogram (Figure 3) in addition to any other pictograms required by its other properties.
  • Category 5 is approximately equivalent by flash point to NFPA Class IIIB combustible liquids as well as NFPA 704 Class 0 (not ignitable). On the SDS, it will include no signal word (unless required by its other properties) and will have pictograms as required by its properties other than flammability or combustibility.

Flammable-Photo2

Flammable-Photo4

 

 

 

 

 

 

 

 

Some key points to know regarding chemicals labeled according to the GHS system, and their SDSs follow:

  • The divisions between the classifications do not match either the U.S. DOT system or the NFPA codes and standards with which we are accustomed.
  • The numbering of the hazard categories in the GHS is opposite that of the NFPA 704 system and the OSHA-compliant Hazardous Materials Identification System.
  • Neither the U.S. DOT nor the U.S. Environmental Protection Agency (EPA) plan, at this time, to adopt the United Nations’ GHS as OSHA has done.
  • The SDS required under the GHS is similar but not identical to the material safety data sheet (MSDS) required under the U.S. DOT and EPA regulations, although it contains all of the required information plus additional data. The GHS-format SDS is also longer than its counterpart under the U.S. DOT. Ten-page SDSs are not uncommon.
  • The U.S. DOT labeling and MSDS regulations are keyed on the single most serious hazard presented by the chemical or product, while the GHS system includes signal words and pictograms for all of the product’s known hazards.
  • The GHS-format SDS will become very common since the U.S. DOT will probably accept it in place of the current formats. The GHS-format SDS contains all of the information that the DOT requires, and includes additional information that is not required at this time by either the OSHA, the U.S. DOT, or the U.S. EPA.
  • Some chemical manufacturers adhere strictly to the GHS SDS standard, while others include additional information such as the classification under NFPA 704.

Emergency service workers need to become familiar with the GHS, its labels, and its SDSs because these are likely to be the information with which we will be given to work when responding to incidents at construction job sites, manufacturing facilities, and business establishments, although some U.S. DOT-compliant information may still be present for some time.

For detailed information on the GHS and basic training materials, visit https://www.osha.gov/dsg/hazcom/index.html.

For samples of GHS-format SDSs, visit the following Web sites:

Note: The references to the Web sites above are included as examples of SDSs only and are not to be understood as endorsements of either products or manufacturers.

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