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What is NFPA 704?

Document #304

The National Fire Protection Association (NFPA) designed NFPA 704 as a standard for the Identification of the Hazards of Materials for Emergency Response. This is commonly known as the NFPA diamond. The four section multicolor diamond shape indicates the health, flammability, instability and related hazards that are presented by short-term, acute exposure to a material during a fire, spill or other emergency-related condition. These identifiers in sign form are found on the outside doors or walls and the inside of many facilities that use chemicals in their daily processes.

The object of this standard is to inform responders to fires, spills or other emergencies of the hazards of the material contained in the facilities.

The standard, which was developed in the early 1950s and tweaked several times since, provides a "simple, recognizable and easily understood system of markings that provides a general idea of the hazards of a material and the severity of these hazards as they relate to emergency response". NFPA 704 1.2.2.

Hazard Symbols

The numerical hazard rating system uses the numbers 0-4, with 4 denoting the highest hazard in that category and 0 indicating a non-hazard. The rating system has three categories, defined by their color. Blue for Health, Red for Flammability and Yellow for Instability. The fourth space at the bottom of the sign is not colored and indicates special hazards. These hazards can include the W symbol with a line through it for water reactive or the OX symbol for materials that may be oxidizers. This space can also be left blank. (Figure 1)

Figure 1

Assignment of Ratings

The assignment of these ratings is to be performed by a technically competent person who is experienced in interpreting the hazard criteria. That person will assign the ratings based on their knowledge of the inherent hazards of those materials. Information on assignment of ratings can be found in Chapter 4 of the standard. It is quite common that when chemicals arrive with their Material Safety Data Sheet (MSDS), the MSDS will have a diamond shape located on it with the ratings already determined. This rating can then be transferred to your sign or used for further determination of the ratings.

Sign Location

The location requirements for signs at your facility are located in Chapter 4 of this standard. Local authorities have jurisdiction as to where and how many are needed, but NFPA suggests as a minimum signs be located in the following locations: (1) Two exterior walls or enclosures containing a means of access to a building or facility (2) Each access to a room or area (3) Each principal means of access to an exterior storage area. Access, configuration, size, location and construction of the building will factor in the location and number of signs required.

The parameters to determine each rating of the health, flammability, instability of the hazards and special notice, which are extensive, are listed in chapters 5, 6, 7 and 8 of the standard. These will help determine the degree of the hazard and how the numerical value is arrived at whether it be a 0, 1, 2, 3 or 4.

A common question regarding the ratings is how to determine a number when you have a variety of different chemicals in the facility. According to NFPA 704 Chapter 4 -, a composite method for determination can be used. This states that a single sign can be used to summarize the maximum ratings contribution by the materials in each category or area. When you have a mixture of chemicals, the MSDS information from each chemical should be used for the determination.

Another common question is "what size should the numbers be?" The numbers should be visible from a minimum distance of 50 ft. The NFPA 704 has the chart below (Figure 2) with recommended distance and letter height requirements.

Figure 2

Distance at which hazard
ratings are legible
Minimum size of
hazard ratings required<
15.24 m (50 ft) 25 mm (1 in.)
22.86 m (75 ft) 51 mm (2 in.)
30.48 m (100 ft) 76 mm (3 in.)
60.96 m (200 ft) 102 mm (4 in.)
91.44 m (300 ft) 152 mm (6 in.)

This overview addresses some of the more common inquiries regarding the NFPA 704 standard. For a more in-depth breakdown and explanation of the criteria to meet this standard, the NFPA can be contacted at or by telephone at 617-770-3000.

Commonly Asked Questions

Q.   Is The NFPA 704 a requirement? Who enforces this requirement?
A.   The NFPA 704 standard is a voluntary standard; each local jurisdiction determines whether or not it will be maintained as a requirement.



NFPA 704 Identification of the Hazards of Materials for Emergency Response - 2010 14th Edition

(Rev. 1/2012)

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Please Note:
The information contained in this publication is intended for general information purposes only and is based on information available as of the initial date of publication. No representation is made that the information or references are complete or remain current. This publication is not a substitute for review of the current applicable government regulations and standards specific to your location and business activity, and should not be construed as legal advice or opinion. Readers with specific questions should refer to the applicable standards or consult with an attorney.

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