What do those diamond-shaped signs on buildings mean?

The National Fire Protection Agency, or NFPA, uses these signs to indicate hazardous materials stored in an unknown building. Listen in to learn how the signs work -- and how they help firefighters -- in this podcast from HowStuffWorks.com.

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Episode Transcript

Speaker 1 (00:00):
Welcome to Brainstuff from house stuff works dot com where
smart happens. Hi. I'm Marshall Brain with today's question. What
do those big diamond shaped signs with red, yellow, and
blue squares on the mean when you see them on

(00:22):
the sides of buildings. You see these signs on any
building that contains hazardous chemicals. The sign is called an
nfp A panel. N f p A stands for the
National Fire Protection Association. The idea behind these signs is
to give firefighters some sort of advanced notice on what
they're getting themselves into when they arrive at the scene

(00:45):
of a fire. When there's a house fire, firefighters have
a pretty good idea of what they're in for, but
if there's a fire at a warehouse in an industrial park,
it is very hard to know what chemicals might be
stored there. The n f p A panel is a
clear indication of what sort of dangers might lie inside.
The panel has four different areas. The red area is

(01:08):
the fire hazard area, the blue is the health hazard area,
the yellow is the reactivity area, and the white is
a specific hazard area. The numbers in the first three
areas range from zero to four, with zero signifying no hazard,
and four signifying a severe hazard. For example, in the

(01:30):
reactivity area, zero means stable, one means unstable if heated,
two means a violent chemical, three means shock or heat
may detonate, and four means may detonate on its own.
In the fire hazard area, the numbers indicate the flash point.
Zero means it won't burn, one means it will burn

(01:53):
above two hundred degrees, two means it will burn below
two hundred degrees, three means it will burn below one degrees,
and four means it will burn below seventy four degrees fahrenheit.
Concrete is an example of a class zero fire hazard.
It won't burn paper and wood, or class one. In

(02:14):
the health hazard area, zero means no hazard, one means
slightly hazard as, two means hazardous, three means extremely hazardous,
and four means deadly. In the specific hazard area, which
is the white square at the bottom of the diamond,
you'll see things like O X Y or oxy for oxidizer,

(02:34):
acid for acids, a O K for alkali, cr for corrosive.
You may also see a W with a bar through
it meaning use no water, or a radiation hazard symbol
for radioactive materials now you can drive around your neighborhood
and get a glimpse into what is stored in all
those buildings. Do you have any ideas or suggestions for

(02:57):
this podcast? If so, please send me an email at
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