Evaluation of Chemical Hazards and Associated Hazard Classifications: What Do the Model Codes Say

Evaluation of Chemical Hazards and Associated Hazard Classifications: What do the model codes say?

By Joseph E. Chacon, PE, TERPconsulting
(This article was originally published in July 2020 in FPE eXTRA, Issue 55.)

Evaluation of chemical hazards and associated hazard classifications can be a complicated and arduous process, with major building and fire code implications. The evaluation of hazards determines the allowable quantity and the resulting occupancy classifications. For example, in the United States, most model codes follow the U.S. Department of Labor Code of Federal Regulations (CFR) – Title 29 definitions for hazardous materials. The model codes separate the hazard classifications into physical and health hazards. The quantities of physical and health hazards is utilized to determine the maximum allowable quantity (MAQ) for each building or control area.

Safety Data Sheets

The safety data sheet (SDS) and all other available information regarding the chemical must be reviewed to accurately determine the hazard classification(s). The International Fire Code (IFC) Appendix E provides guidance for determining hazard categories for common materials. Although not intended for adoption, Appendix E provides information and examples to assist in determining hazard classifications. As noted in this section, the evaluation process is a “strongly subjective process.”

The chemical hazard evaluation process begins with the gathering of information. After as much relevant data as possible has been gathered, the SDS is thoroughly reviewed to determine chemical properties. Careful consideration must be given to each section of the SDS as specific signal words, the concentration of ingredients, and chemical characteristics can change the hazard classification.

Furthermore, it is important to consider multiple hazards as each chemical may contain more than one hazard classification. The reviewer needs to understand the evaluation process to accurately apply the MAQ and other applicable storage and use requirements.

When reviewing the SDS it is imperative to have the IFC or other model code hazard definitions readily available. This will assist in identifying the appropriate hazard classification for the chemical. After each section of the SDS is reviewed, the information can be interpreted, and a hazard classification can be assigned based on the hazard definitions within the code of record.

SDS Section 1 – Identification: Section 1 provides the chemical name and often provides synonyms associated with the chemical. The Chemical Abstract Service (CAS) number is also identified in this section.

SDS Section 2 – Hazard Identification: Although Section 2 of the SDS is labeled “Hazard Identification,” it is important to note that all hazards in accordance with model codes will not appear in this section. Very rarely are the physical and health hazards identified in this section in a straightforward manner. For example, the section may indicate that the material “causes burns on contact with skin.” Although the word “Corrosive” may not appear in this section, this material should be classified as Corrosive based on the ability of the material to “cause visible destruction to living tissue” as defined in the IFC.

This section may also identify the United Nations (UN) Globally Harmonized System (GHS) hazard classifications. It is important to note that the GHS hazard class definitions vary from most model code hazard definitions. The GHS classifications may vary from the fire code but will advise the reviewer of the possible fire code hazards to investigate and identify throughout the remaining sections of the SDS. For example, the GHS classification may identify the material as a “Flammable Liquid – Category 2.” The UN GHS System of Classification and Labelling of Chemicals also known as the “GHS Purple Book” is a valuable resource to determine the UN Categories for GHS hazard classifications. The example above “Flammable Liquid – Category 2” can be identified below:

As shown above “Flammable Liquid – Category 2” most closely resembles the IFC definition of Flammable Liquid Class IB. Although the GHS definition closely correlates to the IFC definition, it is still up to the reviewer to identify the flashpoint and boiling point to determine the applicable fire code classification category.

SDS Section 3 – Composition/Information on ingredients: For certain mixtures hazard classifications may not be as easily identified. The amount and concentration of the material must be carefully considered. It is up to the reviewer to examine all sections of the SDS and all other relevant data to determine the appropriate classifications for the mixture.

SDS Sections 4-8: Sections 4-8 can provide information on health hazards, reactivity hazards, and chemical incompatibilities. These sections are typically used to corroborate hazards identified in other sections of the SDS.

SDS Section 9 – Physical and chemical properties: This section is utilized to determine the chemical state (i.e., solid, liquid, gas). Additionally, this section lists the chemical properties, including boiling point and flashpoint, which are needed to determine the flammability hazard. Other hazard classifications can be obtained from this section including explosive and oxidizing classifications.

SDS Section 10 – Stability and reactivity: This section includes the stability, reactivity, possible hazardous reactions, conditions to avoid, and incompatible materials. The hazard classifications typically determined from this section include Oxidizers, Unstable (Reactive) Materials, and Water-Reactive Materials. The statements contained in this section are closely compared to the IFC definitions to determine the associated hazard classification.

SDS Section 11 – Toxicological information: The numerical values of toxicity are typically found in this section. The LD50 stated in this section is compared to the IFC definitions of Toxic and Highly Toxic. It is important to note that this section may indicate “harmful or toxic if swallowed;” however, the stated LD50 may exceed values provided by the IFC and may not be considered Toxic by IFC definition. The IFC definitions clearly outline the values of the LD50 and LC50 for Toxic and Highly Toxic hazard classifications.

It is also important to note that the GHS classifications may also appear in this section. The GHS classifications again fall outside the definitions provided in the IFC as shown below:

The IFC utilizes classifications of Toxic and Highly Toxic whereas the GHS classifications are categorized as 1-5. These categories can be compared to the IFC definitions to assist in determining the level of toxicity in accordance with the IFC.

SDS Sections 12-16: Sections 12-16 are non-mandatory and may or may not appear on the SDS. These sections may contain transportation hazard classes and other relevant information. The U.S. Department of Transportation (DOT) hazard definitions will vary from most model fire code hazard classifications; however, similarly to the GHS definitions, the DOT classifications will advise the reviewer of the possible fire code hazards to investigate and identify throughout other sections of the SDS.

The Hazardous Materials Identification System (HMIS) ratings may also appear in these sections. Although the HMIS and National Fire Protection Association (NFPA) labeling system may appear quite similar, these rating systems are vastly different. The HMIS system is intended for use by employees and the NFPA ratings are meant primarily for emergency responders.

After reviewing the SDS and other relevant data, the appropriate hazard classification may remain uncertain. If the most appropriate hazard classification remains uncertain it could be necessary to test the material in a laboratory to support contentions that a particular material is or is not a hazard.

NFPA 704 Hazard Rating

After the hazard classifications are assigned to a chemical, the applicable NFPA 704 (Standard System for the Identification of the Hazards of Materials for Emergency Response) hazard ratings must be identified. The NFPA 704 hazard ratings are based on Health, Flammability, Instability, and Special Hazards. The hazard ratings utilize a scale of 0 to 4. The Special Hazards identified in NFPA 704 are W=Water Reactive, OX=Oxidizer, and SA=Simple Asphyxiant. Although many different symbols may be used in the Special Hazards quadrant, these are not considered to be part of the NFPA 704 hazard rating system since the hazards are already represented in the health, flammability, or instability rating categories.

The degree of hazard and criteria is outlined throughout several tables in NFPA 704. The LC50, flashpoint, and other data obtained from the SDS can be compared to the criteria listed in the tables and the associated degree of hazard can be assigned.

As previously mentioned, the Hazardous Material Identification System (HMIS) should not be confused with the NFPA 704 rating. The HMIS system also utilizes colors and numbers to display chemical hazards. The HMIS system is intended to be used by employers and the NFPA 704 label is intended to be used by emergency responders.

Although both hazard communication placards utilize a numbering system, the HMIS numbering system does not always directly translate to the NFPA 704 rating. To accurately determine the NFPA 704 rating, the information in the SDS should be compared to the definitions and tables in NFPA 704.

When assigning a hazard classification to a chemical, all available information must be considered. Another useful tool to identify hazard classifications is hazclass.com. Hazclass.com is an online database of chemicals and their associated hazard classifications that are based on the hazard definitions found in most model fire codes. Hazclass.com should not be used as the sole means of hazard classification, but as a useful tool to identify possible hazard classifications. The website also offers the ability to generate Hazardous Materials Inventory Statement (HMIS) templates based on chemical quantities input by the user.


  1. [1] 29 C.F.R.
  2. [2] International Code Council. “International Fire Code.” Washington, DC, 2018.
  3. [3] UN (2017), Globally Harmonized System of Classification and Labelling of Chemicals (GHS): Seventh Revised Edition, UN, New York, https://doi.org/10.18356/f8fbb7cb-en.
  4. [4] National Fire Protection Association. NFPA 704, Standard System for the Identification of the Hazards of Materials for Emergency Response. Quincy, MA, 2017.