NFPA 704

"NFPA 704: Standard System for the Identification of the Hazards of Materials for
Emergency Response" is a standard maintained by the U.S.-based National Fire Protection
Association. First "tentatively adopted as a guide" in 1960,[1] and revised several times since
then, it defines the "Safety Square" or "Fire Diamond" which is used to quickly and easily
identify the risks posed by hazardous materials. This helps determine what, if any, special
equipment should be used, procedures followed, or precautions taken during the initial stages
of an emergency response. It is an internationally accepted safety standard, and is crucial
while transporting chemicals.

NFPA 704
safety square

4
4 4
W

NFPA 704 safety squares on

containers of ethyl alcohol and
acetone.

Codes

Standard System for the Identification of

the Hazards of Materials for Emergency
Response
The four divisions are typically color-coded with red on top indicating flammability, blue on
the left indicating level of health hazard, yellow on the right for chemical reactivity, and white
containing codes for special hazards. Each of health, flammability and reactivity is rated on a
scale from 0 (no hazard) to 4 (severe hazard). The latest version of NFPA 704 sections 5, 6, 7
and 8 for the specifications of each classification are listed below. The numeric values in the
first column are designated in the standard by "Degree of Hazard" using Arabic numerals (0, 1,
2, 3, 4), not to be confused with other classification systems, such as that in the NFPA 30
Flammable and Combustible Liquids Code, where flammable and combustible liquid
categories are designated by "Class", using Roman numerals (I, II, III).[2]

Flammability (red)
Materials that will not burn under typical fire conditions (e.g., carbon tetrachloride, silicon dioxide,
perfluorohexane, water), including intrinsically noncombustible materials such as concrete, stone, and sand.
0
Materials that will not burn in air unless exposed to a temperature of 820 °C (1,500 °F) for more than
5 minutes.

Materials that require considerable preheating, under all ambient temperature conditions, before ignition and

1 combustion can occur (e.g., mineral oil, ammonia, ethylene glycol). Includes some finely divided suspended
solids that do not require heating before ignition can occur. Flash point at or above 93.3 °C (200 °F).

Must be moderately heated or exposed to relatively high ambient temperature before ignition can occur

2 (e.g., diesel fuel, paper, sulfur and multiple finely divided suspended solids that do not require heating before
ignition can occur). Flash point between 37.8 and 93.3 °C (100 and 200 °F).

Liquids and solids (including finely divided suspended solids) that can be ignited under almost all ambient

3 temperature conditions (e.g., acetone, ethanol). Liquids having a flash point below 22.8 °C (73 °F) and having
a boiling point at or above 37.8 °C (100 °F) or having a flash point between 22.8 and 37.8 °C (73 and 100 °F).

Will rapidly or completely vaporize at normal atmospheric pressure and temperature, or is readily dispersed

4 in air and will burn readily (e.g., gasoline, acetylene, propane, hydrogen gas, diborane). Includes pyrophoric
substances. Flash point below room temperature at 22.8 °C (73 °F).
 Health (blue)
Poses no health hazard, requires no precautions, and would offer no hazard beyond that of ordinary
0
combustible materials (e.g., wood, sugar, salt, propylene glycol)

Exposure would cause irritation with only minor residual injury (e.g., acetone, sodium bromate, potassium
1
chloride)

Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual
2
injury (e.g., diethyl ether, ammonium phosphate, carbon dioxide, chloroform, DEET).

Short exposure could cause serious temporary or moderate residual injury (e.g., liquid hydrogen, sulfuric acid,
3
calcium hypochlorite, carbon monoxide, hexafluorosilicic acid, zinc chloride, sodium hydroxide)

Very short exposure could cause death or major residual injury (e.g. aluminum phosphide, hydrogen cyanide,
4
phosgene, diborane, methyl isocyanate, hydrofluoric acid, sarin, mustard gas)

Instability–reactivity (yellow)

Normally stable, even under fire exposure conditions, and is not reactive with water (e.g., helium, N2, carbon
0
dioxide)

Normally stable, but can become unstable at elevated temperatures and pressures (e.g., propene,
1
ammonium acetate, carbonic acid)

Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or
2
may form explosive mixtures with water (e.g., white phosphorus, potassium, sodium)

Capable of detonation or explosive decomposition but requires a strong initiating source, must be heated

3 under confinement before initiation, reacts explosively with water, or will detonate if severely shocked (e.g.,
ammonium nitrate, caesium, hydrogen peroxide)

Readily capable of detonation or explosive decomposition at normal temperatures and pressures (e.g.,
4
nitroglycerin, chlorine dioxide, nitrogen triiodide, manganese heptoxide, TNT, Picric acid)

Special notice (white)

The white "special notice" area can contain several symbols. The following symbols are defined by the NFPA 704
standard.

Oxidizer, allows chemicals to burn without an air supply (e.g., potassium perchlorate, ammonium nitrate,
OX
hydrogen peroxide).

W Reacts with water in an unusual or dangerous manner (e.g., caesium, sodium, diborane, sulfuric acid).

Simple asphyxiant gas (specifically helium, nitrogen, neon, argon, krypton, and xenon). The SA symbol shall

SA also be used for liquified carbon dioxide vapor withdrawal systems and where large quantities of dry ice are
used in confined areas.[2]
 Non-standard symbols (white)
These hazard codes are not part of the NFPA 704 standard, but are occasionally used in an unofficial manner.
The use of non-standard codes may be permitted, required or disallowed by the authority having jurisdiction
(e.g., fire department).[3]

— No special notice (the correct format is to leave the white square blank, but sometimes a dash is used)

OXY Oxidizer, allows chemicals to burn without an air supply (the correct symbol is "OX")

COR

CORR Corrosive; strong acid or base (e.g., sulfuric acid, potassium hydroxide)

ACID Acid

ALK Alkaline

BIO
Biological hazard (e.g., flu virus, rabies virus)

POI
Poisonous (e.g., strychnine, alpha-amanitin)

RA

RAD
Radioactive (e.g., plutonium, cobalt-60, carbon-14)

CRY
Cryogenic (e.g., liquid nitrogen)
CRYO

G OX Oxygen gas

History

"Fire diamond" of hydrofluosilicic

acid.
The development of NFPA 704 is credited to the Charlotte Fire Department after a fire at the
Charlotte Chemical Company in 1959 led to severe injuries to many of the firefighters.[4][5]
Upon arrival, the fire crew found a fire burning inside a vat that firefighters assumed to be
burning kerosene. The crew tried to suppress the fire, which resulted in the vat exploding due
to metallic sodium being stored in the kerosene. Thirteen firefighters were injured, several of
whom had critical injuries while one lost both ears and most of his face from the incident.

At the time, such vats were not labelled with the materials they contained, so firefighters did
not have the necessary information to recognize that hazardous materials were present,
which required a specific response. In this case, sodium was able to react with water to
release hydrogen gas and large amounts of heat, which has the potential to explode.

The Charlotte Fire Department developed training to respond to fires involving hazardous
materials, ensured that protective clothing was available to those responding, and expanded
the fire prevention inspection program. Fire Marshal J. F. Morris developed the diamond
shaped placard as a marking system to indicate when a building contained hazardous
[6]
materials, with their levels of flammability, reactivity and health effects.

See also

Globally Harmonized System of Classification and Labeling of Chemicals

GHS hazard pictograms

Hazard symbol

HMIS Color Bar

Hazchem

Hazmat

References

1. Dornette, W. H. L.; Woodworth, Miles E. (1969). "Proposed Amendments on Revisions to

the Recommended System for the Identification of The Fire Hazards of Materials / NFPA
No. 704M — 1969" (https://web.archive.org/web/20160303232503/http://www.nfpa.org/
Assets/files/AboutTheCodes/704/TCRF-1975-704M.pdf) (PDF). National Fire Protection
Association. Archived from the original (https://www.nfpa.org/Assets/files/AboutTheCod
es/704/TCRF-1975-704M.pdf) (PDF) on 2016-03-03. Retrieved 2016-03-04.
 2. "NFPA 704: Standard System for the Identification of the Hazards of Materials for
Emergency Response" (https://link.nfpa.org/free-access/publications/704/2022) . 2022.

3. "Decoding the City: The Fire Diamond" (https://www.smithsonianmag.com/arts-culture/

decoding-the-city-the-fire-diamond-18494224/) .

4. "Fact Friday 153 - Charlotte's Haz-Mat History" (https://704shop.com/blogs/fact-friday/f

act-friday-153-charlottes-haz-mat-history) . 704 Shop. 22 June 2018. Retrieved
2022-02-22.

5. "July marks 62 years since Charlotte Fire invented Haz-Mat safety measure" (https://ww
w.fox46.com/news/local-news/july-marks-62-years-since-charlotte-fire-invented-haz-
mat-safety-measure/) . Queen City News. 2021-06-28. Retrieved 2022-02-22.

6. "History of the Charlotte Fire Department" (https://web.archive.org/web/2023040722275

9/https://charlottenc.gov/Fire/about-us/Documents/CFD%20History%20Final%20Jan%2
09%202014.pdf) (PDF). Archived from the original (https://charlottenc.gov/Fire/about-u
s/Documents/CFD%20History%20Final%20Jan%209%202014.pdf) (PDF) on 2023-04-
07. Retrieved 2022-02-22.

External links

NFPA 704 (2022) Free Access (https://link.nfpa.org/free-access/publications/704/2022) on

NFPA.org

"Frequently Asked Questions on NFPA 704" (https://archive.today/20170716160209/http://

www.nfpa.org/assets/files/aboutthecodes/704/704_faqs.pdf) (PDF). Archived from the
original (http://www.nfpa.org/Assets/files/AboutTheCodes/704/704_FAQs.pdf) (PDF) on
2017-07-16. Retrieved 2016-03-04.

"Pamphlet produced by the City of Milwaukee summarizing NFPA 704 code requirements" (h
ttp://www.milwaukee.gov/ImageLibrary/User/dnscms/pdf/broc/hazmat12.pdf) (PDF). City
of Milwaukee.

"Hazard Communication" (https://www.osha.gov/dsg/hazcom/index.html) . Occupational

Safety and Health Administration.

"Safety in the Chemistry Laboratory: NFPA 704 Hazard Identification System" (https://web.ar
chive.org/web/20150310145104/http://chemlabs.uoregon.edu/Safety/NFPA.html) .
University of Oregon. Archived from the original (http://chemlabs.uoregon.edu/Safety/NFP
A.html) on 2015-03-10.
Portal: United States