General Introduction to Fire Sprinkler Systems
Fire protection experts generally agree
that automatic sprinklers represent one of the single, most significant
aspects of a fire management program. Properly designed, installed, and
maintained, these systems can overcome deficiencies in risk management,
building construction, and emergency response. They may also provide
enhanced flexibility of building design and increase the overall level of
The following text presents an overview of fire detection, alarm and
sprinkler systems including system types, components, operations, and
answers to common anxieties.
1: Fire Growth and
Before attempting to understand fire
detection systems and automatic sprinklers, it is beneficial to possess a
basic knowledge of fire development and behavior. With this information, the
role and interaction of these supplemental fire safety systems in the
protection process can then be better realized.
Basically, a fire is a chemical reaction in which a carbon based material
(fuel), mixes with oxygen (usually as a component of air), and is heated to
a point where flammable vapors are produced. These vapors can then come in
contact with something that is hot enough to cause vapor ignition, and a
resulting fire. In simple terms, something that can burn touches something
that is hot, and a fire is produced.
Libraries, archives, museums, and historic structures frequently contain
numerous fuels. These include books, manuscripts, records, artifacts,
combustible interior finishes, cabinets, furnishings, and laboratory
chemicals. It should be recognized that any item containing wood, plastic,
paper, fabric, or combustible liquids is a potential fuel. They also contain
several common, potential ignition sources including any item, action, or
process which produces heat. These encompass electric lighting and power
systems, heating and air conditioning equipment, heat producing conservation
and maintenance activities, and electric office appliance. Flame generating
construction activities such as soldering, brazing, and cutting are frequent
sources of ignition. Arson is unfortunately one of the most common cultural
property ignition sources, and must always be considered in fire safety
When the ignition source contacts the fuel, a fire can start. Following this
contact, the typical accidental fire begins as a slow growth, smoldering
process which may last from a few minutes to several hours. The duration of
this "incipient" period is dependent on a variety of factors including fuel
type, its physical arrangement, and quantity of available oxygen. During
this period heat generation increases, producing light to moderate volumes
of smoke. The characteristic smell of smoke is usually the first indication
that an incipient fire is underway. It is during this stage that early
detection (either human or automatic), followed by a timely response by
qualified fire emergency professionals, can control the fire before
significant losses occur.
As the fire reaches the end of the incipient period, there is usually enough
heat generation to permit the onset of open, visible flames. Once flames
have appeared, the fire changes from a relatively minor situation to a
serious event with rapid flame and heat growth. Ceiling temperatures can
exceed 1,000° C (1,800° F) within the first minutes. These flames can ignite
adjacent combustible contents within the room, and immediately endanger the
lives of the room's occupants. Within 3-5 minutes, the room ceiling acts
like a broiler, raising temperatures high enough to "flash", which
simultaneously ignites all combustibles in the room. At this point, most
contents will be destroyed and human survivability becomes impossible. Smoke
generation in excess of several thousand cubic meters (feet) per minute will
occur, obscuring visibility and impacting contents remote from the fire.
If the building is structurally sound, heat and flames will likely consume
all remaining combustibles and then self extinguish (burn out). However, if
wall and/or ceiling fire resistance is inadequate, (i.e. open doors,
wall/ceiling breaches, combustible building construction), the fire can
spread into adjacent spaces, and start the process over. If the fire remains
uncontrolled, complete destruction or "burn out" of the entire building and
contents may ultimately result.
Successful fire suppression is dependent on extinguishing flames before, or
immediately upon, flaming combustion. Otherwise, the resulting damage may be
too severe to recover from. During the incipient period, a trained person
with portable fire extinguishers may be an effective first line of defense.
However, should an immediate response fail or the fire grow rapidly,
extinguisher capabilities can be surpassed within the first minute. More
powerful suppression methods, either fire department hoses or automatic
systems, then become essential.
A fire can have far reaching impact on the institution's buildings, contents
and mission. General consequences may include:
Most heritage institutions house unique and irreplaceable objects. Fire
generated heat and smoke can severely damage or totally destroy these
items beyond repair.
Operations and mission
damage. Heritage occupancies often contain
educational facilities, conservation laboratories, catalogue services,
administrative/support staff offices, exhibition production, retail, food
service, and a host of other activities. A fire can shut these down with
adverse impact on the organization's mission and its clientele.
Buildings provide the "shell" that safeguards collections, operations and
occupants from weather, pollution, vandalism and numerous other
environmental elements. A fire can destroy walls, floors, ceiling/roof
assemblies and structural support, as well as systems that illuminate,
control temperature and humidity, and supply electrical power. This can in
turn lead to content harm, and expensive relocation activities.
Books, manuscripts, photographs, films, recordings and other archival
collections contain a vast wealth of information that can be destroyed by
Injury or loss of life.
The lives of staff and visitors can be endangered.
Public relations impact.
Staff and visitors expect safe conditions in heritage buildings. Those who
donate or loan collections presume these items will be safeguarded. A
severe fire could shake public confidence and cause a devastating public
A fire represents the single greatest security threat! Given the same
amount of time, an accidental or intentionally set fire can cause far
greater harm to collections than the most accomplished thieves. Immense
volumes of smoke and toxic gases can cause confusion and panic, thereby
creating the ideal opportunity for unlawful entry and theft. Unrestricted
firefighting operations will be necessary, adding to the security risk.
Arson fires set to conceal a crime are common.
To minimize fire risk and its impact,
heritage institutions should develop and implement comprehensive and
objective fire protection programs. Program elements should include fire
prevention efforts, building construction improvements, methods to detect a
developing fire and alert emergency personnel, and means to effectively
extinguish a fire. Each component is important toward overall accomplishment
of the institution's fire safety goal. It is important for management to
outline desired protection objectives during a fire and establish a program
that addresses these goals. Therefore, the basic question to be asked by the
property's managers is, "What maximum fire size and loss can the institution
accept?" With this information, goal oriented protection can be implemented.
2: Fire Detection and
A key aspect of fire protection is to identify a developing fire
emergency in a timely manner, and to alert the building's occupants and fire
emergency organizations. This is the role of fire detection and alarm
systems. Depending on the anticipated fire scenario, building and use type,
number and type of occupants, and criticality of contents and mission, these
systems can provide several main functions. First they provide a means to
identify a developing fire through either manual or automatic methods and
second, they alert building occupants to a fire condition and the need to
evacuate. Another common function is the transmission of an alarm
notification signal to the fire department or other emergency response
organization. They may also shut down electrical, air handling equipment or
special process operations, and they may be used to initiate automatic
suppression systems. This section will describe the basic aspects of fire
detection and alarm systems.
2.2: Control Panels
The control panel is the "brain" of the fire detection and alarm system.
It is responsible for monitoring the various alarm "input" devices such as
manual and automatic detection components, and then activating alarm
"output" devices such as horns, bells, warning lights, emergency telephone
dialers, and building controls. Control panels may range from simple units
with a single input and output zone, to complex computer driven systems that
monitor several buildings over an entire campus. There are two main control
panel arrangements, conventional and addressable, which will be discussed
Conventional or "point wired" fire detection and alarm
systems were for many years the standard method for providing emergency
signaling. In a conventional system one or more circuits are routed through
the protected space or building. Along each circuit, one or more detection
devices are placed. Selection and placement of these detectors is dependent
upon a variety of factors including the need for automatic or manual
initiation, ambient temperature and environmental conditions, the
anticipated type of fire, and the desired speed of response. One or more
device types are commonly located along a circuit to address a variety of
needs and concerns.
Upon fire occurrence, one or more detectors will operate. This action closes
the circuit, which the fire control panel recognizes as an emergency
condition. The panel will then activate one or more signaling circuits to
sound building alarms and summon emergency help. The panel may also send the
signal to another alarm panel so that it can be monitored from a remote
In order to help insure that the system is functioning properly, these
systems monitor the condition of each circuit by sending a small current
through the wires. Should a fault occur, such as due to a wiring break, this
current cannot proceed and is registered as a "trouble" condition. The
indication is a need for service somewhere along the respective circuit.
In a conventional alarm system, all alarm initiating and signaling is
accomplished by the system's hardware which includes multiple sets of wire,
various closing and opening relays, and assorted diodes. Because of this
arrangement, these systems are actually monitoring and controlling circuits,
and not individual devices.
To further explain this, assume that a building's fire alarm system has 5
circuits, zones A through E, and that each circuit has 10 smoke detectors
and 2 manual stations located in various rooms of each zone. A fire ignition
in one of the rooms monitored by zone "A" causes a smoke detector to go into
alarm. This will be reported by the fire alarm control panel as a fire in
circuit or zone "A". It will not indicate the specific detector type nor
location within this zone. Emergency responding personnel may need to search
the entire zone to determine where the device is reporting a fire. Where
zones have several rooms, or concealed spaces, this response can be time
consuming and wasteful of valuable response opportunity.
The advantage of conventional systems is that they are relatively simple
for small to intermediate size buildings. Servicing does not require a large
amount of specialized training.
A disadvantage is that for large buildings, they can be expensive to install
because of the extensive amounts of wire that are necessary to accurately
monitor initiating devices.
Conventional systems may also be inherently labor intensive and expensive to
maintain. Each detection device may require some form of operational test to
verify it is in working condition. Smoke detectors must be periodically
removed, cleaned, and recalibrated to prevent improper operation. With a
conventional system, there is no accurate way of determining which detectors
are in need of servicing. Consequently, each detector must be removed and
serviced, which can be a time consuming, labor intensive, and costly
endeavor. If a fault occurs, the "trouble" indication only states that the
circuit has failed, but does not specifically state where the problem is
occurring. Subsequently, technicians must survey the entire circuit to
identify the problem.
Addressable or "intelligent" systems represent the current
state-of-the-art in fire detection and alarm technology. Unlike conventional
alarm methods, these systems monitor and control the capabilities of each
alarm initiating and signaling device through microprocessors and system
software. In effect, each intelligent fire alarm system is a small computer
overseeing and operating a series of input and output devices.
Like a conventional system, the address system consists of one or more
circuits that radiate throughout the space or building. Also, like standard
systems, one or more alarm initiating devices may be located along these
circuits. The major difference between system types involves the way in
which each device is monitored. In an addressable system, each initiating
device (automatic detector, manual station, sprinkler water flow switch,
etc.) is given a specific identification or "address". This address is
correspondingly programmed into the control panel's memory with information
such as the type of device, its location, and specific response details such
as which alarm devices are to be activated.
The control panel's microprocessor sends a constant interrogation signal
over each circuit, in which each initiating device is contacted to inquire
its status (normal or emergency). This active monitoring process occurs in
rapid succession, providing system updates every 5 to 10 seconds.
The addressable system also monitors the condition of each circuit,
identifying any faults which may occur. One of the advancements offered by
these systems is their ability to specifically identify where a fault has
developed. Therefore, instead of merely showing a fault along a wire, they
will indicate the location of the problem. This permits faster diagnosis of
the trouble, and allows a quicker repair and return to normal.
Advantages provided by addressable alarm systems include stability, enhanced
maintenance, and ease of modification. Stability is achieved by the system
software. If a detector recognizes a condition which could be indicative of
a fire, the control panel will first attempt a quick reset. For most
spurious situations such as insects, dust, or breezes, the incident will
often remedy itself during this reset procedure, thereby reducing the
probability of false alarm. If a genuine smoke or fire condition exists, the
detector will reenter the alarm mode immediately after the reset attempt.
The control panel will now regard this as a fire condition, and will enter
its alarm mode.
With respect to maintenance, these systems offer several key advantages over
conventional ones. First of all, they are able to monitor the status of each
detector. As a detector becomes dirty, the microprocessor recognizes a
decreased capability, and provides a maintenance alert. This feature, known
as Listed Integral Sensitivity Testing, allows facilities personnel to
service only those detectors that need attention, rather than requiring a
labor and time consuming cleaning of all units.
Advanced systems, such as the FCI 7200 incorporate another maintenance
feature known as drift compensation. This software procedure adjusts the
detector's sensitivity to compensate for minor dust conditions. This avoids
the ultra sensitive or "hot" detector condition which often results as
debris obscures the detector's optics. When the detector has been
compensated to its limit, the control panel alerts maintenance personnel so
that servicing can be performed.
Modifying these systems, such as to add or delete a detector, involves
connecting or removing the respective device from the addressable circuit,
and changing the appropriate memory section. This memory change is
accomplished either at the panel or on a personal computer, with the
information downloaded into the panel's microprocessor.
The main disadvantage of addressable systems is that each system has its own
unique operating characteristics. Therefore, service technicians must be
trained for the respective system. The training program is usually a 3-4 day
course at the respective manufacturer's facility. Periodic update training
may be necessary as new service methods are developed.
2.3: Fire Detectors
When present, humans can be excellent fire detectors. The healthy person
is able to sense multiple aspects of a fire including the heat, flames,
smoke, and odors. For this reason, most fire alarm systems are designed with
one or more manual alarm activation devices to be used by the person who
discovers a fire. Unfortunately, a person can also be an unreliable
detection method since they may not be present when a fire starts, may not
raise an alarm in an effective manner, or may not be in perfect heath to
recognize fire signatures. It is for this reason that a variety of automatic
fire detectors have been developed. Automatic detectors are meant to imitate
one or more of the human senses of touch, smell or sight. Thermal detectors
are similar to our ability to identify high temperatures, smoke detectors
replicate the sense of smell, and flame detectors are electronic eyes. The
properly selected and installed automatic detector can be a highly reliable
Manual fire detection is the oldest method of detection. In
the simplest form, a person yelling can provide fire warning. In buildings,
however, a person's voice may not always transmit throughout the structure.
For this reason, manual alarm stations are installed. The general design
philosophy is to place stations within reach along paths of escape. It is
for this reason that they can usually be found near exit doors in corridors
and large rooms.
The advantage of manual alarm stations is that, upon discovering the fire,
they provide occupants with a readily identifiable means to activate the
building fire alarm system. The alarm system can then serve in lieu of the
shouting person's voice. They are simple devices, and can be highly reliable
when the building is occupied. The key disadvantage of manual stations is
that they will not work when the building is unoccupied. They may also be
used for malicious alarm activations. Nonetheless, they are an important
component in any fire alarm system.
Thermal detectors are the oldest type of automatic
detection device, having origin in the mid 1800's, with several styles still
in production today. The most common units are fixed temperature devices
that operate when the room reaches a predetermined temperature (usually in
the 135°-165°F/57°-74°C). The second most common type of thermal sensor is
the rate-of-rise detector, which identifies an abnormally fast temperature
climb over a short time period. Both of these units are "spot type"
detectors, which means that they are periodically spaced along a ceiling or
high on a wall. The third detector type is the fixed temperature line type
detector, which consists of two cables and an insulated sheathing that is
designed to breakdown when exposed to heat. The advantage of line type over
spot detection is that thermal sensing density can be increased at lower
Thermal detectors are highly reliable and have good resistance to operation
from non-hostile sources. They are also very easy and inexpensive to
maintain. On the down side, they do not function until room temperatures
have reached a substantial temperature, at which point the fire is well
underway and damage is growing exponentially. Subsequently, thermal
detectors are usually not permitted in life safety applications. They are
also not recommended in locations where there is a desire to identify a fire
before substantial flames occur, such as spaces where high value thermal
sensitive contents are housed.
Smoke detectors are a much newer technology, having gained
wide usage during the 1970's and 1980's in residential and life safety
applications. As the name implies, these devices are designed to identify a
fire while in its smoldering or early flame stages, replicating the human
sense of smell. The most common smoke detectors are spot type units, that
are placed along ceilings or high on walls in a manner similar to spot
thermal units. They operate on either an ionization or photoelectric
principle, with each type having advantages in different applications. For
large open spaces such as galleries and atria, a frequently used smoke
detector is a projected beam unit. This detector consists of two components,
a light transmitter and a receiver, that are mounted at some distance (up to
300 ft/100m) apart. As smoke migrates between the two components, the
transmitted light beam becomes obstructed and the receiver is no longer able
to see the full beam intensity. This is interpreted as a smoke condition,
and the alarm activation signal is transmitted to the fire alarm panel.
A third type of smoke detector, which has become widely used in extremely
sensitive applications, is the air aspirating system. This device consists
of two main components: a control unit that houses the detection chamber, an
aspiration fan and operation circuitry; and a network of sampling tubes or
pipes. Along the pipes are a series of ports that are designed to permit air
to enter the tubes and be transported to the detector. Under normal
conditions, the detector constantly draws an air sample into the detection
chamber, via the pipe network. The sample is analyzed for the existence of
smoke, and then returned to atmosphere. If smoke becomes present in the
sample, it is detected and an alarm signal is transmitted to the main fire
alarm control panel. Air aspirating detectors are extremely sensitive and
are typically the fastest responding automatic detection method. Many high
technology organizations, such as telephone companies, have standardized on
aspiration systems. In cultural properties they are used for areas such as
collections storage vaults and highly valuable rooms. These are also
frequently used in aesthetically sensitive applications since components are
often easier to conceal, when compared to other detection methods.
The key advantage of smoke detectors is their ability to identify a fire
while it is still in its incipient. As such, they provide added opportunity
for emergency personnel to respond and control the developing fire before
severe damage occurs. They are usually the preferred detection method in
life safety and high content value applications. The disadvantage of smoke
detectors is that they are usually more expensive to install, when compared
to thermal sensors, and are more resistant to inadvertent alarms. However,
when properly selected and designed, they can be highly reliable with a very
low probability of false alarm.
Flame detectors represent the third major type of automatic
detection method, and imitate the human sense of sight. They are line of
sight devices that operate on either an infrared, ultraviolet or combination
principle. As radiant energy in the approximate 4,000 to 7,700 angstroms
range occurs, as indicative of a flaming condition, their sensing equipment
recognizes the fire signature and sends a signal to the fire alarm panel.
The advantage of flame detection is that it is extremely reliable in a
hostile environment. They are usually used in high value energy and
transportation applications where other detectors would be subject to
spurious activation. Common uses include locomotive and aircraft maintenance
facilities, refineries and fuel loading platforms, and mines. A disadvantage
is that they can be very expensive and labor intensive to maintain. Flame
detectors must be looking directly at the fire source, unlike thermal and
smoke detectors which can identify migrating fire signatures. Their use in
cultural properties is extremely limited.
2.4: Alarm Output Devices
Upon receiving an alarm notification, the fire alarm control panel must
now tell someone that an emergency is underway. This is the primary function
of the alarm output aspect of a system. Occupant signaling components
include various audible and visual alerting components, and are the primary
alarm output devices. Bells are the most common and familiar alarm sounding
device, and are appropriate for most building applications. Horns are
another option, and are especially well suited to areas where a loud signal
is needed such as library stacks, and architecturally sensitive buildings
where devices need partial concealment. Chimes may be used where a soft
alarm tone is preferred, such as health care facilities and theaters.
Speakers are the fourth alarm sounding option, which sound a reproducible
signal such as a recorded voice message. They are often ideally suited for
large, multistory or other similar buildings where phased evacuation is
preferred. Speakers also offer the added flexibility of emergency public
address announcements. With respect to visual alert, there are a number of
strobe and flashing light devices. Visual alerting is required in spaces
where ambient noise levels are high enough to preclude hearing sounding
equipment, and where hearing impaired occupants may be found. Standards such
as the Americans with Disabilities Act (ADA) mandate visual devices in
numerous museum, library, and historic building applications.
Another key function of the output function is emergency response
notification. The most common arrangement is an automatic telephone or radio
signal that is communicated to a constantly staffed monitoring center. Upon
receiving the alert, the center will then contact the appropriate fire
department, providing information about the location of alarm. In some
instances, the monitoring station may be the police or fire departments, or
a 911 center. In other instances it will be a private monitoring company
that is under contract to the organization. In many cultural properties, the
building's in house security service may serve as the monitoring center.
Other output functions include shutting down electrical equipment such as
computers, shutting off air handling fans to prevent smoke migration, and
shutting down operations such as chemical movement through piping in the
alarmed area. They may also activate fans to extract smoke, which is a
common function in large atria spaces. These systems can also activate
discharge of gaseous fire extinguishing systems, or pre-action sprinkler
In summary, there are several options for a building's fire detection and
alarm system. The ultimate system type, and selected components, will be
dependent upon the building construction and value, its use or uses, the
type of occupants, mandated standards, content value, and mission
sensitivity. Contacting a fire engineer or other appropriate professional
who understands fire problems and the different alarm and detection options
is usually a preferred first step to find the best system.
3: Fire Sprinklers
For most fires, water represents the ideal
extinguishing agent. Fire sprinklers utilize water by direct application
onto flames and heat, which causes cooling of the combustion process and
prevents ignition of adjacent combustibles. They are most effective during
the fire's initial flame growth stage, while the fire is relatively easy to
control. A properly selected sprinkler will detect the fire's heat, initiate
alarm, and begin suppression within moments after flames appear. In most
instances sprinklers will control fire advancement within a few minutes of
their activation, which will in turn result in significantly less damage
than otherwise would happen without sprinklers.
Among the potential benefits of sprinklers are the following:
and control of a developing fire. Sprinkler
systems respond at all times, including periods of low occupancy. Control
is generally instantaneous.
In conjunction with the building fire alarm system, automatic sprinkler
systems will notify occupants and emergency response personnel of the
Reduced heat and smoke
damage. Significantly less heat and smoke
will be generated when the fire is extinguished at an early stage.
Enhanced life safety.
Staff, visitors and fire fighters will be
subject to less danger when fire growth is checked.
Egress route and fire/smoke barrier placement becomes less restrictive
since early fire control minimizes demand on these systems. Many fire and
building codes will permit design and operations flexibility based on the
presence of a fire sprinkler system.
A sprinkler controlled fire can reduce demand on security forces by
minimizing intrusion and theft opportunities.
expenditure. Sprinkler controlled fires are
less damaging than fires in non-sprinkled buildings. Insurance
underwriters may offer reduced premiums in sprinkler protected properties.
These benefits should be considered when
deciding on the selection of automatic fire sprinkler protection.
3.2: Sprinkler System
Components and Operation
Sprinkler systems are essentially a series of water pipes that are
supplied by a reliable water supply. At selected intervals along these pipes
are independent, heat activated valves known as sprinkler heads. It is the
sprinkler that is responsible for water distribution onto the fire. Most
sprinkler systems also include an alarm to alert occupants and emergency
forces when sprinkler activation (fire) occurs.
During the incipient fire stage, the heat output is relatively low and is
unable to cause sprinkler operation. However, as the fire intensity
increases, the sprinkler's sensing elements become exposed to elevated
temperatures (typically in excess of 57-107°C (135-225°F), and begin to
deform. Assuming temperatures remain high, as they would during an
increasing fire, the element will fatigue after an approximate 30 to 120
second period. This releases the sprinkler's seals allowing water to
discharge onto the fire and begin the suppression action. In most situations
less than 2 sprinklers are needed to control the fire. In fast growing fire
scenarios, however, such as a flammable liquid spill, up to 12 sprinklers
may be required.
In addition to normal fire control efforts, sprinkler operation may be
interconnected to initiate building and fire department alarms, shutdown
electrical and mechanical equipment, close fire doors and dampers, and
suspend some processes.
As fire fighters arrive their efforts will focus on ensuring that the system
has contained the fire, and, when satisfied, shut off the water flow to
minimize water damage. It is at this point that staff will normally be
permitted to enter the damaged space and perform salvage duties.
3.3: System Components and
The basic components of a sprinkler
system are the sprinklers, system piping, and a dependable water source.
Most systems also require an alarm, system control valves, and means to test
The sprinkler itself is the spray nozzle, which distributes water over a
defined fire hazard area (typically 14-21 m2/150-225 ft2)
with each sprinkler operating by actuation of its own temperature linkage.
The typical sprinkler consists of a frame, thermal operated linkage, cap,
orifice, and deflector. Styles of each component may vary but the basic
principles of each remain the same.
The frame provides the main structural component which holds the sprinkler
together. Water supply piping is connected to the sprinkler at the base of
the frame. The frame holds the thermal linkage and cap in place, and
supports the deflector during discharge. Frame styles include standard and
low profile, flush, and concealed mount. Some are designed for extended
spray coverage, beyond the range of normal sprinklers. Standard finishes
include brass, chrome, black, and white, while custom finishes are
available for aesthetically sensitive spaces. Special coatings are
available for areas subject to high corrosive effect. Selection of a
specific frame style is dependent on the size and type of area to be
covered, anticipated hazard, visual impact features, and atmospheric
The thermal linkage is the component that controls water release. Under
normal conditions the linkage holds the cap in place and prevents water
flow. As the link is exposed to heat, however, it weakens and releases the
cap. Common linkage styles include soldered metal levers, frangible glass
bulbs, and solder pellets. Each link style is equally dependable.
Upon reaching the desired operating
temperature, an approximate 30 second to 4 minute time lag will follow. This
lag is the time required for linkage fatigue and is largely controlled by
the link materials and mass. Standard responding sprinklers operate closer
to the 3-4 minute mark while quick response (QR) sprinklers operate in
significantly shorter periods. Selection of a sprinkler response
characteristic is dependent upon the existing risk, acceptable loss level,
and desired response action.
In heritage applications the advantage of quick response sprinklers often
becomes apparent. The faster a sprinkler reacts to a fire, the sooner the
suppression activity is initiated, and the lower the potential damage level.
This is particularly beneficial in high value or life safety applications
where the earliest possible extinguishment is a fire protection goal. It is
important to understand that response time is independent of response
temperature. A quicker responding sprinkler will not activate at a lower
temperature than a comparable standard head.
The cap provides the water tight seal which is located over the sprinkler
orifice. It is held in place by the thermal linkage, and falls from
position after linkage heating to permit water flow. Caps are constructed
solely of metal or a metal with a Teflon disk.
The machined opening at the base of the sprinkler frame is the orifice
from which extinguishing water flows. Most orifice openings are 15 mm (1/2
inch) diameter with smaller bores available for residential applications
and larger openings for higher hazards.
The deflector is mounted on the frame opposite the
orifice. Its purpose is to break up the water stream discharging from the
orifice into a more efficient extinguishing pattern. Deflector styles
determine how the sprinkler is mounted, with common sprinkler mounting
styles known as upright (mounted above the pipe), pendent (mounted below
the pipe, i.e. under ceilings), and sidewall sprinklers which discharge
water in a lateral position from a wall. The sprinkler must be mounted as
designed to ensure proper action. Selection of a particular style is often
dependent upon physical building constraints.
A sprinkler that has received wide spread
interest for museum applications is the on/off sprinkler. The principle
behind these products is that as a fire occurs, water discharge and
extinguishing action will happen similar to standard sprinklers. As the room
temperature is cooled to a safer level, a bimetallic snap disk on the
sprinkler closes and water flow ceases. Should the fire reignite, operation
will once again occur. The advantage of on/off sprinklers is their ability
to shut off, which theoretically can reduce the quantity of water
distributed and resultant damage levels. The problem, however, is the long
time period that may pass before room temperatures are sufficiently cooled
to the sprinkler's shut off point. In most heritage applications, the
building's construction will retain heat and prevent the desired sprinkler
shut down. Frequently, fire emergency response forces will have arrived and
will be able to close sprinkler zone control valves before the automatic
shut down feature has functioned.
On-off sprinklers typically cost 8-10 times more than the average sprinkler,
which is only justifiable when assurance can be made that these products
will perform as intended. Therefore, on/off sprinkler use in heritage
facilities should remain limited.
Selection of specific sprinklers is based on: risk characteristics, ambient
room temperature, desired response time, hazard criticality and aesthetic
factors. Several sprinkler types may be used in a heritage facility.
All sprinkler systems require a reliable water source. In urban areas, a
piped public service is the most common supply, while rural areas generally
utilize private tanks, reservoirs, lakes, or rivers. Where a high degree of
reliability is desired, or a single source is undependable, multiple
supplies may be utilized.
Basic water source criteria include:
The source must be
available at all times. Fires can happen at
any time and therefore, the water supply must be in a constant state of
readiness. Supplies must be evaluated for resistance to pipe failure,
pressure loss, droughts, and other issues that may impact availability.
The system must provide
adequate sprinkler supply and pressure. A
sprinkler system will create a hydraulic demand, in terms of flow and
pressure, on the water supply. The supply must be capable of meeting this
demand. Otherwise, supplemental components such as a fire pump or standby
tank must be added to the system.
The supply must provide
water for the anticipated fire duration.
Depending of the fire hazard, suppression may take several minutes to over
an hour. The selected source must be capable of providing sprinklers with
water until suppression has been achieved.
The system must provide
water for fire department hoses operating in tandem with the sprinkler
system. Most fire department procedures
involve the use of fire attack hoses to supplement sprinklers. The water
supply must be capable of handling this additional demand without adverse
impact on sprinkler performance.
Sprinkler water is transported to fire via
a system of fixed pipes and fittings. Piping material options include
various steel alloys, copper, and fire resistant plastics. Steel is the
traditional material with copper and plastics utilized in many sensitive
Primary considerations for selection of pipe materials include:
Ease of installation.
The easier the material is installed, the less disruption is imposed on
the institution's operations and mission. The ability to install a system
with the least amount of disturbance is an important consideration,
especially in sprinkler retrofit applications where building use will
continue during construction.
Cost of material versus
cost of protected area. Piping typically
represents the greatest single cost item in a sprinkler system. Often
there is a temptation to reduce costs by utilizing less expensive piping
materials that may be perfectly acceptable in certain instances, i.e.
office or commercial environs. However, in heritage applications where the
value of contents may be far beyond sprinkler costs, appropriateness of
the piping rather than cost should be the deciding factor.
with materials. A mistake to be avoided is
one in which the contractor and pipe materials have been selected, only to
find out that the contractor is inexperienced with the pipe. This can lead
to installation difficulties, added expense, and increased failure
potential. A contractor must demonstrate familiarity with the desired
material before selection.
requirements or other installation constraints.
In some instances, such as in fine art vaults, requirements may be imposed
to limit the amount of work time in the space. This will often require
extensive prefabrication work outside of the work area. Some materials are
easily adapted to prefabrication.
Some pipe materials are cleaner to install than others. This will reduce
the potential for soiling collections, displays, or building finishes
during installation. Various materials are also resistant to accumulation
in the system water, which could discharge onto collections. Cleanliness
of installation and discharge should be a consideration.
Some pipe materials are heavier or more cumbersome to work with than
others. Consequently additional workers are needed to install pipes, which
can add to installation costs. If the number of construction workers
allowed into the building is a factor, lighter materials may be
The benefits and disadvantages of each
material should be evaluated prior to selection of pipe materials.
Other major sprinkler system components include:
A sprinkler system must be capable of shut down after the fire has been
controlled, and for periodic maintenance and modification. In the simplest
system a single shutoff valve may be located at the point where the water
supply enters the building. In larger buildings the sprinkler system may
consist of multiple zones with a control valve for each. Control valves
should be located in readily identified locations to assist responded
Alarms alert building occupants and emergency forces when a
sprinkler water flow occurs. The simplest alarms are water driven gongs
supplied by the sprinkler system. Electrical flow and pressure switches,
connected to a building fire alarm system, are more common in large
buildings. Alarms are also provided to alert building management when a
sprinkler valve is closed.
Drain and test
connections. Most sprinkler systems have
provisions to drain pipes during system maintenance. Drains should be
properly installed to remove all water from the sprinkler system, and
prevent water from leakage onto protected spaces, when piping service is
necessary. It is advisable to install drains at a remote location from the
supply, thereby permitting effective system flushing to remove debris.
Test connections are usually provided to simulate the flow of a sprinkler,
thereby verifying the working condition of alarms. Test connections should
be operated every 6 months.
Dry pipe and pre-action sprinkler systems require complex, special control
valves that are designed to hold water from the system piping until
needed. These control valves also include air pressure maintenance
equipment and emergency operation/release systems.
Fire Hose Connections.
Fire fighters will often supplement sprinkler systems with hoses.
Firefighting tasks are enhanced by installing hose connections to
sprinkler system piping. The additional water demand imposed by these
hoses must be factored into the overall sprinkler design in order to
prevent adverse system performance.
3.4: System Types
There are three basic types of sprinkler
systems: wet pipe, dry pipe and pre-action, with each having applicability,
depending on a variety of conditions such as potential fire severity,
anticipated fire growth rates, content water sensitivity, ambient
conditions, and desired response. In large multifunction facilities, such as
a major museum or library, two or more system types may be employed.
Wet pipe systems are the most common sprinkler system. As the name implies,
a wet pipe system is one in which water is constantly maintained within the
sprinkler piping. When a sprinkler activates this water is immediately
discharged onto the fire.
Wet pipe system advantages include:
System simplicity and
reliability. Wet pipe sprinkler systems
have the least number of components and therefore, the lowest number of
items to malfunction. This produces unexcelled reliability, which is
important since sprinklers may be asked to sit in waiting for many years
before they are needed. This simplicity aspect also becomes important in
facilities where system maintenance may not be performed with the desired
Relative low installation
and maintenance expense. Due to their
overall simplicity, wet pipe sprinklers require the least amount of
installation time and capital. Maintenance cost savings are also realized
since less service time is generally required, compared to other system
types. These savings become important when maintenance budgets are
Ease of modification.
Heritage institutions are often dynamic with respect to exhibition and
operation spaces. Wet pipe systems are advantageous since modifications
involve shutting down the water supply, draining pipes, and making
alterations. Following the work, the system is pressure tested and
restored. Additional work for detection and special control equipment is
avoided, which again saves time and expense.
Short term down time
following a fire. Wet pipe sprinkler
systems require the least amount of effort to restore. In most instances,
sprinkler protection is reinstated by replacing the fused sprinklers and
turning the water supply back on. Pre-action and dry pipe systems may
require additional effort to reset control equipment.
The main disadvantage of these systems is
that they are not suited for subfreezing environments. There also may be
concern where piping is subject to severe impact damage, such as some
The advantages of wet systems make them highly desirable for use in most
heritage applications, and with limited exception, they represent the system
of choice for museum, library and historic building protection.
The next system type, a dry pipe sprinkler system, is one in which pipes are
filled with pressurized air or nitrogen, rather than water. This air holds a
remote valve, known as a dry pipe valve, in a closed position. The dry pipe
valve is located in a heated area and prevents water from entering the pipe
until a fire causes one or more sprinklers to operate. Once this happens,
the air escapes and the dry pipe valve releases. Water then enters the pipe,
flowing through open sprinklers onto the fire.
The main advantage of dry pipe sprinkler systems is their ability to provide
automatic protection in spaces where freezing is possible. Typical dry pipe
installations include unheated warehouses and attics, outside exposed
loading docks and within commercial freezers.
Many heritage managers view dry pipe sprinklers as advantageous for
protection of collections and other water sensitive areas, with a perceived
benefit that a physically damaged wet pipe system will leak while dry pipe
systems will not. In these situations, however, dry pipe systems will
generally not offer any advantage over wet pipe systems. Should impact
damage happen, there will only be a mild discharge delay, i.e. 1 minute,
while air in the piping is released before water flow.
Dry pipe systems have some disadvantages that must be evaluated before
selecting this equipment. These include:
Dry pipe systems require additional control equipment and air pressure
supply components, which increases system complexity. Without proper
maintenance this equipment may be less reliable than a comparable wet pipe
Higher installation and
maintenance costs. The added complexity
impacts the overall dry pipe installation cost. This complexity also
increases maintenance expenditure, primarily due to added service labor
Lower design flexibility.
There are strict requirements regarding the maximum permitted size
(typically 750 gallons) of individual dry pipe systems. These limitations
may impact the ability of an owner to make system additions.
Increased fire response
time. Up to 60 seconds may pass from the
time a sprinkler opens until water is discharged onto the fire. This will
delay fire extinguishing actions, which may produce increased content
potential. Following operation, dry pipe
sprinkler systems must be completely drained and dried. Otherwise,
remaining water may cause pipe corrosion and premature failure. This is
not a problem with wet pipe systems where water is constantly maintained
With the exception of unheated building
spaces and freezer rooms, dry pipe systems do not offer any significant
advantages over wet pipe systems and their use in heritage buildings is
generally not recommended.
The third sprinkler system type, preaction, employs the basic concept of a
dry pipe system in that water is not normally contained within the pipes.
The difference, however, is that water is held from piping by an
electrically operated valve, known as a preaction valve. The operation of
this valve is controlled by independent flame, heat, or smoke detection. Two
separate events must happen to initiate sprinkler discharge. First, the
detection system must identify a developing fire and then open the preaction
valve. This allows water to flow into system piping, which effectively
creates a wet pipe sprinkler system. Second, individual sprinkler heads must
release to permit water flow onto the fire.
In some instances, the preaction system may be set up with an interlock
feature in which pressurized air or nitrogen is added to system piping. The
purpose of this feature is twofold: first to monitor piping for leaks and
second to hold water from system piping in the event of inadvertent detector
operation. The most common application for this system type is in freezer
The primary advantage of a preaction system is the dual action required for
water release: the preaction valve must operate and sprinkler heads must
fuse. This provides an added level of protection against inadvertent
discharge, and for this reason, these systems are frequently employed in
water sensitive environments such as archival vaults, fine art storage
rooms, rare book libraries and computer centers.
There are some disadvantages to preaction systems. These include:
Higher installation and
maintenance costs. Preaction systems are
more complex with several additional components, notably a fire detection
system. This adds to the overall system cost.
As with drypipe systems, preaction sprinkler systems have specific size
limitations which may impact future system modifications. In addition,
system modifications must incorporate changes to the fire detection and
control system to ensure proper operation.
reliability. The higher level of complexity
associated with preaction systems creates an increased chance that
something may not work when needed. Regular maintenance is essential to
ensure reliability. Therefore, if the facility's management decides to
install preaction sprinkler protection, they must remain committed to
installing the highest quality equipment, and to maintaining these systems
as required by manufacturer's recommendations.
Provided the application is appropriate,
preaction systems have a place in heritage buildings, especially in water
A slight variation of preaction sprinklers is the deluge system, which is
basically a preaction system using open sprinklers. Operation of the fire
detection system releases a deluge valve, which in turn produces immediate
water flow through all sprinklers in a given area. Typical deluge systems
applications are found in specialized industrial situations, i.e. aircraft
hangers and chemical plants, where high velocity suppression is necessary to
prevent fire spread. Use of deluge systems in heritage facilities is rare
and typically not recommended.
Another preaction system variation is the on/off system which utilizes the
basic arrangement of a preaction system, with the addition of a thermal
detector and nonlatching alarm panel. The system functions similar to any
other preaction sprinkler system, except that as the fire is extinguished, a
thermal device cools to allow the control panel to shut off water flow. If
the fire should reignite, the system will turn back on. In certain
applications on/off systems can be effective. Care, however, must be
exercised when selecting this equipment to ensure that it functions as
desired. In most urban areas, it is likely that the fire department will
arrive before the system has shut itself down, thereby defeating any actual
3.5: Sprinkler Concerns
Several common misconceptions about
sprinkler systems exist. Consequently, heritage building owners and
operators are often reluctant to provide this protection, especially for
collections storage and other water sensitive spaces. Typical
When one sprinkler
operates, all will activate. With the
exception of deluge systems (discussed later in this leaflet), only those
sprinklers in direct contact with the fire's heat will react.
Statistically, approximately 61% of all sprinkler controlled fires are
stopped by two or less sprinklers.
Sprinklers operate when
exposed to smoke. Sprinklers function by
thermal impact against their sensing elements. The presence of smoke alone
will not cause activation without high heat.
Sprinkler systems are
prone to leakage or inadvertent operation.
Insurance statistics indicate a failure rate of approximately 1 head
failure per 16,000,000 sprinklers installed per year. Sprinkler components
and systems are among the most tested systems in an average building.
Failure of a proper system is very remote.
Where failures do occur, they are usually
the result of improper design, installation, or maintenance. Therefore, to
avoid problems, the institution should carefully select those who will be
responsible for the installation and be committed to proper system
Sprinkler activation will
cause excessive water damage to contents and structure.
Water damage will occur when a sprinkler activates. This
issue becomes relative, however, when compared to alternative suppression
methods. The typical sprinkler will discharge approximately 25 gallons per
minute (GPM) while the typical fire department hose delivers 100-250 GPM.
Sprinklers are significantly less damaging than hoses. Since sprinklers
usually operate before the fire becomes large, the overall water quantity
required for control is lower than situations where the fire continues to
increase until firefighters arrive.
The table below shows approximate
comparative water application rates for various manual and automatic
Table 31: Fire Suppression Water
Portable Fire Extinguisher/Appliance
Occupant Use Fire Hose
Fire Department, Single 1.5" Hose
Fire Department, Double 1.5" Hose
Fire Department, Single 2.5" Hose
Fire Department, Double 2.5" Hose
One final point to consider is that the water damage is usually capable of
repair and restoration. Burned out contents, however, are often beyond mend.
Sprinkler systems look bad
and will harm the building's appearance.
This concern has usually resulted from someone who has observed a less
than ideal appearing system, and admittedly there are some poorly designed
systems out there. Sprinkler systems can be designed and installed with
almost no aesthetic impact.
To ensure proper design, the institution
and design team should take an active role in the selection of visible
components. Sprinkler piping should be placed, either concealed or in a
decorative arrangement, to minimize visual impact. Only sprinklers with high
quality finishes should be used. Often sprinkler manufacturers will use
customer provided paints to match finish colors, while maintaining the
sprinkler's listing. The selected sprinkler contractor must understand the
role of aesthetics.
To help ensure overall success, the sprinkler system designer should
understand the institution's protection objectives, operations, and fire
risks. This individual should be knowledgeable about system requirements and
flexible to implement unique, thought-out solutions for those areas where
special aesthetic or operations concerns exist. The designer should be
experienced in the design of systems in architecturally sensitive
Ideally, the sprinkler contractor should be experienced working in heritage
applications. However, an option is to select a contractor experienced in
water sensitive applications such as telecommunications, pharmaceuticals,
clean rooms, or high tech manufacturing. Companies including AT&T, Bristol
Meyers Squibb, and IBM have very stringent sprinkler installation
requirements. If a sprinkler contractor has demonstrated success with these
type of organizations, then they will be capable of performing
satisfactorily in a heritage site.
The selected sprinkler components should be provided by a reputable
manufacturer, experienced in special, water sensitive hazards. The cost
differential between average and the highest quality components is minimal.
The long term benefit, however, is substantial. When considering the value
of a facility and its contents, the extra investment is worth while.
With proper attention to selection, design, and maintenance, sprinkler
systems will serve the institution without adverse impact. If the
institution or design team does not possess the experience to ensure the
system is proper, a fire protection engineer experienced in heritage
applications can be a great advantage.
3.6: Water Mist
One of the most promising automatic
extinguishing technologies is the recently available fine water droplet, or
mist systems. This technology represents another tool that can provide
automatic fire suppression in some cultural property applications. Potential
uses include locations where reliable water supplies do not exist, where
even sprinkler water discharges are too high, or where building construction
and aesthetics impact the use of standard sprinkler pipe dimensions. Mist
systems may also be an appropriate solution to the protection void left by
the environmental concerns, and subsequent demise, of Halon 1301 gas.
Mist technology was originally developed for offshore uses such as on board
ships and oil drilling platforms. For both of these applications, there is a
need to control severe fires while limiting the amount of extinguishing
water, which could impact vessel stability. These systems have been
extensively approved by a number of domestic and international marine
organizations, and have been a protection standard for the past 8-10 years.
They have a solid track record dealing with maritime fires. These systems
have also been used in several land based applications, and have a number of
listings, primarily in Europe, where their effectiveness has been
recognized. Some systems have recently received approvals for North American
land based uses.
Mist systems discharge limited water quantities at higher pressures than
sprinkler systems. These pressures range from approximately 100 to 1,000 psi,
with the higher pressure systems generally producing larger volumes of fine
sprays. The produced droplets are usually in the 50 to 200 micron diameter
range (compared to 600-1,000 microns for standard sprinklers), resulting in
exceptionally high efficiency cooling and fire control, with significantly
little water. In most situations, fires are controlled with approximately
10-25% of the water normally associated with sprinklers. Water saturation
that is often associated with standard firefighting procedures is decreased.
Other benefits include lower aesthetic impact and known environmental
Typical water mist systems consist of the following components:
Water for a system may be provided by either the piped building system or
a dedicated tank arrangement. In some instances, lower pressure systems
may use existing sprinkler piping. For most, however, supplemental pumps
will be required. Other options include dedicated water/nitrogen storage
cylinders, which can deliver a limited duration supply.
Piping and nozzles:
Piping can be greatly reduced when compared to sprinklers. For low
pressure systems, pipes are generally 25-50% smaller than comparable
sprinkler piping. For high pressure systems, piping is even smaller with
the 0.50-0.75 inch diameters as the norm. Like sprinklers, nozzles are
individually activated by the fire's heat, and are selected to cover a
certain size hazard. Their sizes are comparable to a low profile
Detection and control
equipment. In some instances, mist
discharge can be controlled by selected, high reliability intelligent
detectors or by an advanced technology VESDA smoke detection system. These
systems represent the premier, state-of-the-art, fire detection technology
that can provide very early warning of a developing fire, as well as
reduce the probability of inadvertent discharge.
At this point, one of the main drawbacks to
mist systems is their higher cost, which can be 50-100% greater than
standard sprinklers. This cost, however, may be reduced due to possible
installation labor savings. In rural applications, where reliable sprinkler
water supplies can be expensive, mist systems may be comparable or less than
standard sprinklers. Another problem is that these systems do not have the
variety of approvals and listings commonly associated with sprinklers. As
such, they may not be as recognized by fire and building authorities. In
addition, the number of contractors who are familiar with the technology is
limited. These concerns are diminishing, however, as use of these systems
becomes more widespread.
In summary, automatic sprinklers often represent one of the most
important fire protection options for most heritage applications. The
successful application of sprinklers is dependent upon careful design and
installation of high quality components by capable engineers and
contractors. A properly selected, designed and installed system will offer
unexcelled reliability. Sprinkler system components should be selected for
compliance with the institution's objectives. Wet pipe systems offer the
greatest degree of reliability and are the most appropriate system type for
most heritage fire risks. With the exception of spaces subject to freezing
conditions, dry pipe systems do not offer advantages over wet pipe systems
in heritage buildings. Preaction sprinkler systems are beneficial in areas
of highest water sensitivity. Their success is dependent upon selection of
proper suppression and detection components and management's commitment to
properly maintain systems. Water mist represents a very promising
alternative to gaseous agent systems.
1999, Northeast Document Conservation Center. All rights reserved.
To discuss residential or business
sprinkler systems, call (281) 855-1970,