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For industrial,
commercial and institutional facilities that manufacture, process,
use or store hazardous materials, the NFPA 704 Marking System
provides a readily recognized, easily understood system for
identifying specific hazards and their severity.
Using spatial, visual, and numerical methods to describe in simple
terms the relative hazards of a material, it addresses the health,
flammability, instability, and related hazards that may be presented
as short-term, acute exposures that are most likely to occur as a
result of fire, spill or similar emergency.
The diamond shaped or “on-point square” diagram gives at a glance a
general idea of the inherent hazards and the order of severity of
these hazards under emergency conditions such as spills, leaks and
fires. The diagram identifies the “Health,” “Flammability,” and
“Reactivity” hazards of materials and indicates the order of
severity of each hazard by the use of numerical
gradings, from four (4), indicating severe hazard or extreme danger,
to blank, indicating no required warning.
In the diamond-shaped diagram, the “health” hazard is identified at
the left with a blue background, “Flammability” at the top with a
red background and “Reactivity” at the right with a yellow
background.
The bottom space is used to identify special hazards important to
emergency response personnel and has a white background. Additional
special hazards are listed in rectangular white boxes below the
placard.
The placard warning system number for each hazard category will be
selected according
to the following criteria:
HEALTH
4. Materials that have an inhalation Threshold Limit Value (TLV) or
Permissible Exposure Limit (PEL) of less than 100 parts per million
(PPM) and on skin contact can be absorbed through the skin to create
a poisonous effect on the body.
3. All other materials that have an inhalation TLV or PEL of less
then 100 ppm and may on skin contact create an irritating or burning
effect on the exposed skin.
2. Materials that have an inhalation TLV or PEL from 100 to 1000 ppm
and may on skin contact create an irritating effect on the exposed
skin.
1. Materials that have an inhalation TLV or PEL over 1000 but under
5000 ppm.
FLAMMABILITY
4. All flammable gases and liquids with a flash point below -45 F.
3. All flammable gases or liquids with flash points from -45 F to
100 F.
2. All combustible liquids or solids with flash points from 101 F to
140 F.
1. All combustible liquids with flash points from 141 F to 300 F.
REACTIVITY
4. Materials readily capable of detonation or explosive reaction at
normal temperatures and pressures. Includes materials that are very
sensitive to heat, shock or light.
3. Materials that when heated and under confinement are capable of
detonation and which may react violently with water. A “W” should
appear as a special hazard notice if an explosive reaction with
water can be expected.
2. Materials that will undergo a violent chemical change at elevated
temperatures and pressures but do not detonate. A “W” should appear
as a special hazard if with water may cause a violent reaction or
may cause potentially explosive mixtures to be formed.
1. Materials that are normally stable, but may become unstable in
combination with other materials or at elevated temperatures and
pressures. A “W” should appear as a special hazard if a vigorous but
not violent reaction with water may take place.
SPECIAL HAZARDS
Special hazard symbols such as W (water reactive), OXY (oxidizing
material), CRY (cryogenic material), COR (corrosive material), POI
(poisonous material) or the radiation warning symbol will be added
to the white bottom section of the placard when available
information indicates that
one of these special hazards exist. When multiple special hazards
exist, white panels will be added below the placard to list the
additional special hazards that apply.
Amount of Hazard
Determine the need for facility placards by comparing the total
amount of material
with the same hazard category number to the amount requiring
placarding as specified for each hazard category number.
Facility and building placards identify the highest hazard rating in
each category based on the combined materials in a category rating
exceeding threshold quantities.
After the health category number for the facility is determined, use
the same process to determine the flammability and reactivity
categories. If none of the numbering requirements
for a category are met, the category is left without a number and
only the background hazard category color shows.
Determine the need to placard subdivisions or rooms within the
facility by comparing the amounts of materials that are used or
stored in that area with the amounts requiring placarding for each
hazard category number.
Placards that are placed to identify the hazards in area
subdivisions due to storage or process shall be affixed next to
access points into the subdivisions. These placards must be visible
when doors into subdivisions are open or closed.
FSM
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