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Fire Sprinkler Systems
How Fire Sprinkler Systems
Work
BY DANIELLE FISHER
You've
probably seen a number of movies where a small amount of smoke triggers all of
the sprinklers in a building, soaking everyone and everything inside.
But
did you know that sprinklers aren't even triggered by smoke, and they don't all
go off at once?
Fire sprinkler
systems are actually heat activated, one sprinkler head at a time, and most
fires usually require only one or two sprinklers to be extinguished.
These
are just two of the many misconceptions about fire sprinkler systems. In this
article, we'll dispel other myths and learn the ins and outs of this important
safety technology.
You
might think installing a fire sprinkler system is like choosing water damage
over fire damage. This belief is a spinoff from the myths we just mentioned --
that sprinklers are activated by smoke and every sprinkler head goes off at the
same time.
If
that were the case, sprinkler systems could potentially cause more harm than
good.
After
all, if you burned a piece of toast, every sprinkler would go off, soaking all
of your belongings, even though there never was any real danger of fire.
Fortunately,
the clever engineers who developed these systems designed them to reduce the
damage to your property from water, smoke and fire.
Fire
sprinkler systems have been around for more than two centuries and have seen
significant improvements over the years.
It's
true that early versions weren't very reliable and caused significant water
damage. But today, sprinkler systems are credited with reducing deaths and loss
of property by more than 65 percent [source: Fleming].
Since
each sprinkler head is automatically triggered by fire-specific temperature,
just one or two sprinklers can quickly extinguish and/or contain a fire to the
room where it started and cause little property damage.
And
because sprinklers use about six times less water than a fire hose, they're
actually less harmful to your property than a visit from the fire department.
Fire Sprinklers as Fire Prevention Systems
You've
heard about the importance of a properly maintained smoke detector. You've
probably also heard the annoying beeping noise it makes when it needs some
attention.
Have
you also heard that a smoke detector is all you need for fire protection?
If so, you've heard another one of the most common myths regarding fire
sprinkler systems: We don't need them if we have a smoke detector.
Some
even believe that smoke detectors can put out fires. They cannot.
Smoke
detectors are designed to alert us to a potential fire, and in cases where
they're hooked up to an alarm system, alert the fire department.
They're
an important part of a fire prevention system, as are fire sprinklers. The
presence of one does not cancel out the need for the other. They work together
to save life and property from fire.
When a fire starts, the resulting smoke will
eventually set off a smoke detector alerting residents to danger.
This
process can be quite slow depending on where the smoke detector is located.
Meanwhile, the fire is growing.
Alerting
residents to the presence of fire is important. But, so is putting the fire
out.
When
a fire starts, it quickly heats the air directly above it. This air rises and
is pushed out to either side when it hits the ceiling. As this hot air reaches
a sprinkler head, that sprinkler head is activated.
Not just any heat source will trigger a sprinkler
system to activate. The sprinkler heads must detect a high enough temperature
-- usually between 135 and 165 degrees Fahrenheit (57 to 74 Celsius).
Most
sprinkler heads are equipped with a glass trigger filled with a glycerin-based
liquid that expands at the appropriate temperature, breaking the glass and
activating the sprinkler head.
The
sprinkler head is attached to a system of pipes that are hidden behind the walls
or ceiling. These pipes wind through the building and outside to connect with a
reliable water source.
When
the sprinkler head is triggered, a valve to the pipe system is opened,
releasing the water that is kept under pressure from the pipes.
The
water is quickly pushed out of the pipes through the sprinkler head, spraying
water downward and out to the sides. This carefully designed spray of water
extinguishes the fire below and prevents it from spreading.
Fire sprinkler systems have revolutionized fire safety
by automatically putting out fires in the room of origin and preventing fires
from spreading or re-igniting.
The
amount of time this process requires depends on the type of fire sprinkler
system.
Types
of Fire Sprinkler Systems
Because
fire sprinkler systems protect a variety of buildings and property, many
different types have been developed over the years.
These
include wet, dry, deluge, pre-action and foam. Each has its own unique set of
characteristics that protect the specific building and property for which it
was installed.
As we learned on the previous page, sprinkler heads
are connected to a system of pipes in the walls or ceiling of a room.
These
pipes are composed of steel, copper or fire-resistant plastic.
The
most commonly used system in commercial buildings is a wet pipe system, which is composed of steel pipes
that are always filled with water (hence, the term "wet").
The
water in the pipes is under a moderate amount of pressure.
When
the sprinkler head is activated, the pressurized water in the pipes is
immediately released, providing a faster reaction time than any other type of
system.
The wet pipe system is also the simplest and most
reliable, boasting cost savings for easy installation and low maintenance.
However,
wet pipe systems are not always the best choice.
Since
the pipes are always filled with water, they're not recommended for locations
where the pipes might freeze or in residential environments where accidental
leaks could be detrimental.
As you might have guessed, in a dry pipe system, the pipes are not filled
with water -- they're actually filled with compressed air.
When
the sprinkler head is activated, a valve releases the compressed air through
the sprinkler head. Once all of the air is released, the pressure in the pipe
changes, allowing water to fill the system.
Dry
pipe systems have a slower reaction time (up to a minute delay). To make up for
this, dry pipe systems release a larger amount of extremely pressurized water,
which requires larger pipes (and a larger budget).
And,
while a leaky pipe in a dry pipe system doesn't pose a flooding threat,
maintenance to the system is more complicated and costly.
So,
this type of system isn't recommended unless specific conditions -- an unheated
warehouse in Canada, for example -- exist.
MORE FIRE SAFETY TIPS
Even if your warehouse, office building or apartment is equipped
with an automatic sprinkler system, be sure you have operating smoke detectors,
as well. And have at least one on every floor. They cost on average less than
$10 and save thousands of lives every year. Just remember to change the
batteries at least twice a year.
.
Dry
Pipe Fire Sprinkler Systems
Pre-action
and deluge systems are variations of the dry pipe system.
Pre-action
systems must be triggered twice
before water is dispensed from the sprinkler head. The first trigger --
usually a smoke detector or a heat detector that is separate from the sprinkler
head -- allows water into the pipes.
Once
this trigger occurs, the system acts like a wet pipe system.
The
second trigger, the individual sprinkler heads, releases the water, pushing it
through the sprinkler head to extinguish the fire.
This
type of system provides added protection against false sprinkler head
activation.
If
a sprinkler head is falsely triggered, an alarm will sound, but no water will
be released, since the pipes remain dry until the second trigger has been
activated.
Although
sprinkler heads are not likely to accidentally activate -- sprinkler heads have
a one in 16 million false activation rate -- pre-action systems are very
popular when dealing with sensitive property like in a museum or library [source: USFA].
In deluge systems, like the pre-action system, water
enters the pipes when triggered by a heat or smoke detector, separate from the
sprinkler heads.
There
may also be a manual function, where pushing a button or pulling a cord
activates the system.
The
sprinkler heads in a deluge system are open, meaning they don't have a trigger
function and are activated simultaneously.
Deluge
systems are usually installed in chemical plants or other areas where the
spread of fire would be exceptionally hazardous.
The widespread use of fire sprinkler systems and the
resulting innovations are no doubt a result of laws, regulations and building
codes that require their installation.
Fire
Sprinklers and Building Codes
Fire sprinkler
systems have been in use for more than 100 years. This is no doubt a result of
codes and regulations, requiring the use of these systems in public buildings.
Codes
and regulations that require the installation of fire sprinkler systems were
first put into place in the 1960s [source: Fleming].
Before
then, builders mainly installed sprinklers to reduce property loss and
insurance costs.
After
collecting staggering statistics comparing the fire death rate in
sprinkler-protected buildings versus non-protected, the fire sprinkler industry
began a push for updated building codes to require the installation of these
systems.
Today, building codes in many countries require the
installation of fire sprinkler systems, although the United States has the
highest record of systems installed.
These
codes are usually based on generic code sets developed by building associations
and other reputable organizations such as the International Code Council, the
National Fire Protection Agency (NFPA) and the U.S. Fire Administration (USFA).
Once
adopted, these generic codes are locally amended. In the United States,
building codes are set by city and state governments.
Code sets usually require the installation of fire
sprinkler systems across the board for new construction of high rises and
commercial buildings.
Retro-fit
codes are becoming more popular. Some of the old, existing building types that
now require sprinklers include hotels, nursing homes and dormitories.
You
can find out more about your area's codes for fire sprinkler systems by
visiting your local government's Web site. Or visit www.nfpa.org for a free copy of the NFPA
5000 code set.
The USFA Web site has many helpful resources
as well, including a list of fire sprinkler protected hotels.
Unfortunately, even though most fire deaths occur in
homes, codes have not yet been put into effect requiring fire sprinkler system
installation in single-family homes.
THE WINECOFF HOTEL FIRE
In 1913, and just a year after the
"unsinkable" Titanic sank, the 15-story "absolutely
fireproof" Winecoff Hotel in Atlanta was built without a fire
sprinkler system, smoke detectors or fire escape ladders. Then more than 30
years later in December 1946, a massive fire broke out in the hotel, killing
119 guests, including 30 teenage boys, who had no means of escape. The tragedy,
which is still the deadliest hotel fire in the United States, led to immediate
national fire and safety codes that are still strictly enforced [source: NFPA].
Sprinkler
Systems at Home
According
to the American Fire Sprinkler Association, a home fire occurs every 79
seconds. A 2009 National Fire Protection Association study reports that 3,000
deaths a year can be attributed to fires in homes [source: Figueroa].
Given
these startling statistics and what we've already learned about the life- and
property-saving characteristics of fire sprinkler system installation, it's
hard to believe that less than 2 percent of homes in the United States have
fire sprinkler systems [source: Hall].
So
why are homeowners hesitant to install a system that could save their lives and
property?
While
aesthetics shouldn't outweigh life safety, one reason many single-family
homeowners don't want to install sprinkler systems is that they believe
sprinkler heads are an eye sore.
Fortunately,
new designs for residential systems are actually quite undetectable, and many
can be installed flush to the ceiling.
Flush
sprinkler heads are hidden behind a metal panel that hides the sprinkler head,
but still allows it to spray normally.
And
residential sprinklers are smaller than commercial ones and require less water.
They're
typically dry pipe systems, providing added protection against potential water
damage that could occur during home improvements or other home accidents.
Additionally,
since the development of residential systems is a newer concept, their designs
include many new innovations (like improved sensitivity), making them faster
than commercial sprinklers.
Perhaps
the most common myth about home sprinkler systems is that they're expensive.
Not
only is the installation of a home fire sprinkler system affordable, it can
drastically decrease your home owner's insurance premium.
Considering
installation costs, reduced insurance rates and potential property destruction
costs, a 2007 National Institute of Standards and Technology found the addition
of a home sprinkler system could produce up to $4,800 in savings.
Home
systems will only continue to become more cost-effective as they become more
common. Don't be surprised if you're required to install sprinkler systems in
your home at some point in the future.
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