Hazardous Materials Identification

There are boundless amounts of hazardous materials that present increased risks to people exposed to them, whether building occupants, people in nearby structures, or first responders. These materials vary greatly in their composition and physical states. The risks, or hazards, associated with these materials are even more varied and must be assessed for a particular material in the state and manner in which it will be stored or handled. With such a wide range of materials and hazards there is also great diversity in construction requirements, fire protection systems, handling and operations, and response tactics associated with these materials. Here we will focus on the system of markings that provides a general idea of how hazardous materials need to be identified.

What is a Hazardous Material?

Before discussing the specifics of hazardous materials identification, it can be beneficial to know what is considered a hazardous material. Hazardous materials are defined in NFPA codes and standards as chemicals or substances that are classified as a physical hazard or a health hazard. Physical hazard materials are those classified as an explosive, flammable cryogen, flammable gas, flammable solid, ignitible liquid, organic peroxide, oxidizer, oxidizing cryogen, pyrophoric, unstable (reactive), or water-reactive material. Health hazard materials are those classified as a toxic, highly toxic, or corrosive material.

How do hazardous materials need to be identified?

NFPA 704, Standard System for the Identification of the Hazards of Materials for Emergency Response, specifies the identification requirements for these materials. NFPA 704 applies when another Federal, state or local regulation or code requires its use. NFPA 704 does not specify when a container, tank or facility must be labeled rather it specifies how to label when another code, standard or an AHJ (Authority Having Jurisdiction, such as the local fire department) requires such labeling. The standard applies to industrial, commercial, and institutional facilities that manufacture, process, use, or store hazardous materials. It does not apply to transportation, use by the general public, and a few other specific uses.

The purpose of the standard is to provide a simple, readily recognized, and easily understood system of markings that provides a general idea of the hazards of a material and the severity of the hazards as they relate to emergency response. The identification system specified in NFPA 704 is intended to enable first responders to easily decide whether to evacuate the area or to commence emergency control procedures and to also provide information to assist in selecting firefighting tactics and emergency procedures.

The NFPA 704 hazard identification system is characterized by a diamond which is more precisely defined as a “square-on-point” shape. It identifies the degree of severity of the health, flammability, and instability hazards. Hazard severity is indicated by a numerical rating that ranges from zero (0) indicating a minimal hazard, to four (4) indicating a severe hazard. The hazards are arranged spatially such that health hazards are indicated in the nine o’clock position, flammability at the twelve o’clock position, and instability at the three o’clock position. The six o’clock position on the symbol represents special hazards and has a white background; it is not always filled.


Water reactivity (avoid the use of water)




Simple asphyxiant (nitrogen, helium, neon, krypton, or xenon)


As an example, the following would be used for propane gas which has a moderate health hazard, a severe flammability hazard, is normally stable, and does not require any special labeling. Another example is for liquid oxygen which can present a serious health hazard under emergency conditions, is not flammable, is stable, and is an oxidizer.\


Propane ID 


Where do signs need to be located?

The placard is meant to provide quick hazard information for emergency responders. It should be visible in case of an emergency where the responders are likely to enter. If there are numerous areas where the responders could enter the facility, there should be numerous placards. The placement and quantity should be decided using a facility’s best judgment coupled with the advice from your AHJ. At a minimum the placard should be posted on the two exterior walls of a facility or building, each access to a room or area, or each principal means of access to an exterior storage area.

Other Considerations

As mentioned at the start of this discussion there are many additional considerations regarding hazardous materials. Even within this topic of identification there is a lot more to it than what has been simplified in this blog. Check out this collection of NFPA 704 frequently asked questions for more information. Beyond that there are construction, maximum allowable quantities, fire protection system, and worker exposure requirements just to name a few. Additionally, each of these will vary based on the nature of the material(s) being stored or used. If you want more detail on identification or any of the other topics around hazardous materials, let us know in the comments.

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Jonathan Hart
Technical Lead, Principal Engineer at NFPA

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