If there’s an emergency, will first responders immediately know that hazardous chemicals are used or stored in your facility?

If there’s an emergency, will first responders immediately know that hazardous chemicals are used or stored in your facility?

Will they know if they can work safely in the area using only specialized protective equipment? Will they know if a chemical reacts with water in a dangerous way?

Critical questions like these in situations that demand snap decisions need to be answered quickly. And they are, without a word spoken, by the National Fire Protection Association (NFPA®) 704 rating system (commonly referred to as the NFPA hazard diamond or fire diamond). The NFPA 704 diamond system alerts firefighters and other emergency response personnel to the health, flammability and reactivity hazards present and special considerations needed to effectively fight a fire, spill or other dangerous situation involving hazardous chemicals.

Explore the background of the NFPA diamond, its colors, numbers and legends, as well as sizing and placement as recommended by the NFPA 704 Standard.[1]

Designed to deliver critical information quickly

The NFPA diamond alerts emergency responders to the presence of hazardous materials and their potential effects, and helps them plan an appropriate emergency response. It does not identify specific chemicals in the facility or chronic, long-term health hazards as a result of them.

The NFPA 704 diamond system has applications in commercial, industrial and institutional facilities that manufacture, process, use or store hazardous materials. It can also assist engineers as well as plant and safety personnel in taking inventory and evaluating the relative hazards of materials in their facility.[2]

You’ve seen the fire diamond, even if you’re not a safety professional

The NFPA diamond has been a recognizable symbol for decades, ever since its creation in 1960.[3] Anyone who works with or near hazardous and potentially dangerous chemicals or materials will most likely have seen the NFPA hazard diamond on building entrances, exterior walls or storage areas. But even when it comes to the general public, the fire diamond is widespread on semi-trucks, propane tanks, train cars and other places where potentially hazardous materials are stored or transported.

Image of a NFPA label on the side of a tank

The NFPA 704 system is a standard, not a code

If you’re asking yourself “Do I need to use the fire diamond?”, the answer is: “It depends.” Because it’s a standard, the NFPA 704 system tells you how to label, not when. A local Authority Having Jurisdiction (AHJ), e.g., a fire department, determines requirements by adopting the standard and making it law. So, you should always check with your local AHJ for requirements of where and when to apply NFPA 704 labels.

However, due to its beneficial and simplistic design, many facilities voluntarily place appropriate NFPA fire diamonds on buildings and locations where hazardous materials are stored or used to assist local responders in the event of an emergency and help safeguard against injury—hence its prevalence in many environments.

Elements of the NFPA diamond

The NFPA 704 system is referred to as the fire diamond due to its square-on-point orientation. It’s comprised of four smaller diamonds, each distinguished by color, placement and symbol (numerical or text). The hazard numbers range from 0 (no hazard) to 4 (severe hazard).

An individual technically competent and experienced in the interpretation of the hazard criteria as set forth in Chapters 5 through 8 of the NFPA 704 standard should perform a hazard evaluation.[1] These qualified individuals determine the ratings for a material by comparing data from the manufacturer‐supplied MSDS to the criteria set forth in the NFPA 704 Standard.

Here’s a snapshot of the hazard degree definition associated with each diamond as laid out by the NFPA 704 Standard[1] as well as potential examples of chemicals that may be associated with each rating. Always consult a chemical’s material safety data sheet (MSDS) when determining ratings.

  • Health Hazard (blue, left diamond or 9 o’clock)

    When looking at the NFPA 704 diamond, the left diamond is blue and relates to the level of hazard to a person’s body. A chemical’s health hazard number indicates the level as to which it can cause personal injury via inhalation, skin or eye contact, or ingestion. It does not include potential injury resulting from fire or explosion, or from chronic long-term exposure.


Flammability Hazard (red, top diamond or 12 o’clock)

The top diamond is red. It communicates to responders a chemical’s flammability hazard, or the degree of susceptibility of a material to burning.


Instability Hazard (yellow, right diamond or 3 o’clock)

When looking at the NFPA fire diamond, the right diamond is yellow and indicates a chemical’s instability hazard. This number details a degree of reaction with ambient air, light or both, and the degree of intrinsic susceptibility of materials to release energy by self-reaction. Responding personnel will use this number to determine if:

  • The area shall be evacuated
  • A fire shall be fought from a protected location
  • Caution should be used in approaching a spill or fire to apply extinguishing agents[1]
  • Special Hazards (white, bottom diamond or 6 o’clock)

    The white area can contain one of several special notice symbols defined by the NFPA 704 Standard:

    NFPA Diamond with the white diamond highlighted and the others grayed out

    • OX – Oxidizer, allows chemicals to burn without an air supply (e.g., ammonium nitrate)
    • W – Reacts with water in an unusual or dangerous manner (e.g., sulfuric acid)
    • SA – Simple asphyxiant gas (e.g., neon). This is also used for liquified carbon dioxide vapor withdrawal systems and where large quantities of dry ice are used in confined areas

    You may see other symbols in the special hazard area, though they are not listed as part of the NFPA 704 Standard. These could include:

    • COR (corrosive)
    • ACID
    • ALK (alkaline)
    • BIO (biological)
    • POI (poisonous)
    • RA or RAD (radioactive)
    • CRY or CRYO (cryogenic)

Location of the NFPA diamond varies

When display of the NFPA 704 diamond is a requirement, placement and quantity will be determined by an AHJ. Generally speaking, these guidelines may adhere to the following criteria:

  • Visible in case of an emergency where responders are likely to enter
  • Numerous placards in numerous areas
  • At a minimum: two exterior walls of a facility or building, each entryway to a room or area, or each principal means of access to an exterior storage area[2]

See Chapter 4.3 of NFPA 704 for further guidance.[1]

Sizing up the NFPA diamond

NFPA 704 diamond size will relate to the minimum distance at which it should be visible, which will be part of an AHJ’s requirements. See Chapter 9 of the NFPA 704 Standard for specific size requirements at certain distances.[1]

Previously Featured on Brady's website.


1“NFPA 704: Standard System for the Identification of the Hazards of Materials for Emergency Response.” NFPA, s-and-standards/all-codes-and-standards/list-of-codes-and-standards/detail?code=704. Accessed 21 July 2021.
2“Frequently Asked Questions on NFPA 704.” NFPA, Accessed 21 July 2021.
3“Report of Committee on Fire Hazards of Materials.” NFPA, Accessed 21 July 2021.

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