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Nuisance Fire Alarms and the AHJ
Ronald H. Kirby
Vice President, Industry Relations
Simplex
In most organizations, both public and private, people are being asked to do more with
less; the fire service is no exception. That's why the early warning provided by automatic
fire detection and alarm systems is more important than ever. And yet, in the NFPA codes
and standards development process, some proposals for fire detection provoke negative
comments that allude to a so-called nuisance alarm problem. Certainly, at a time when the
fire service is also experiencing cutbacks in resources, the consequences of nuisance
alarms is exacerbated, so controlling them becomes even more critical. Fortunately, today
there is absolutely no reason for any jurisdiction to tolerate nuisance alarms from a fire
alarm system; AHJs have the means at their disposal to significantly reduce, if not
eliminate, this problem.
In this article the term "nuisance alarm" is used to describe any situation
where occupants are evacuated from a building and/or the fire service is dispatched to a
building in response to an alarm from a fire detection and alarm system when there is no
hostile fire. In this article the term "nuisance alarm" includes false alarms,
unwanted alarms and unnecessary alarms.
Nuisance alarms are costly to the fire service absorbing fire department resources.
Nuisance alarms are demoralizing and potentially dangerous to fire fighters. Nuisance
alarms are disruptive to building occupants and can, over time, cause occupants to ignore
all alarms. Of course, failure to respond to an actual alarm can have terrible
consequences.
Causes of Nuisance Alarms
Nuisance alarms can result from a number of causes, but mostly stem from faulty equipment,
misapplication of equipment, vandalism and external phenomena such as lightning storms.
Whatever the cause, however, nuisance alarms can be dramatically reduced if not
eliminated; however, this will not usually happen without the active involvement of the
Authority Having Jurisdiction.
The Role of Technology in Combating Nuisance Alarms
It is safe to say that fire alarm systems being installed today are virtually free from
nuisance alarms mainly because of advances in technology. Analog smoke detectors have made
a significant contribution to eliminating nuisance alarms. Dirt build-up in smoke
detectors is a major cause of nuisance alarms. As dirt builds up over time in detectors,
it tends to make them more sensitive.
This increased sensitivity causes the activation of dirty detectors by trace particles of
ambient smoke which normally wouldn't activate clean detectors. Transient conditions, such
as Radio Frequency Interference from, for example, cellular telephones, that would not
affect a clean detector, might activate a more sensitive dirty detector. Many analog
systems have a feature called drift compensation, which automatically filters out the
effects of dirt that contribute to false alarms. Many analog smoke detection systems
provide an automatic indication at the control panel when individual automatic smoke
detectors need cleaning.
In some systems the data transmitted from analog fire detectors to the fire alarm control
panel is digitized, making information less subject to the contamination from RFI and
electrical transients, which can lead to nuisance alarms. The sensitivity of each smoke
detector is individually adjustable from the analog system control panel. This means that
locations such as elevator lobbies which might have ambient tobacco smoke can have
detectors with lower sensitivity than those in a computer room, for example. This
customizing of smoke detector sensitivity settings can help reduce nuisance alarms without
compromising detection speed in applications where low sensitivity is unnecessary.
Nuisance Alarms from Existing Systems
Most nuisance alarms from existing fire alarm systems probably originate from smoke
detectors, with improper application being a frequent cause. Smoke detectors installed in
places such as kitchens, furnace rooms or loading docks where smoke is found under normal
conditions can be expected to cause nuisance alarms.
As mentioned above, dirty smoke detectors are a major cause of nuisance alarms and the
issue is not if they will get dirty, but when. Smoke detector components can degrade over
time making them unstable and more prone to nuisance alarms from such sources as
walkie-talkies.
Some older smoke detectors lacked adequate protection against insect infestation. These
detectors can be seasonably troublesome in environments where small spiders or mites are
present.
Electrical disturbances can cause nuisance alarms. Disturbances can result from surges on
the utility company's power lines, but are usually the result of electric storms and the
resultant lightning strikes.
Some nuisance alarms are the result of mischief or vandalism when misguided people operate
manual fire alarm boxes for amusement.
Actions to Eliminate Nuisance Alarms from Smoke Detectors on Old Systems
Where smoke detectors have been installed in improper locations, relocate them.
Tables A-5-3.6.1.2(a) and A-5-3.6.1.2(b) in 1996 NFPA 72 – The National Fire Alarm Code
provide extensive guidance on situations where the use of smoke detectors should be
avoided.
In some rare instances heat detectors should be substituted for smoke detectors. For
example, smoke detectors on loading docks where engine exhaust is likely to be present
should be replaced with heat detectors. Bear in mind that this substitution should not be
made in life safety applications since heat detectors are for property protection and are
not life safety devices.
In some instances substituting a smoke detector utilizing ionization technology for a
detector with photoelectric technology (or vice versa) can eliminate a false alarm
problem. For example, most ionization detectors are less likely to alarm from steam than
are photoelectric detectors. Therefore, a nuisance alarm problem from a photoelectric
detector near a shower or above a janitor's sink might be eliminated by removing the
photoelectric detector and installing an ionization detector in its place.
Paragraph 7-3.2.1 in 1993 NFPA 72 – The National Fire Alarm Code requires that the
sensitivity of smoke detectors be periodically tested. Smoke detectors found to be outside
of their listed sensitivity rating should be cleaned, and programs should be established
to clean detectors installed in dirty locations on a regularly scheduled basis.
As a general rule, smoke detectors which have been installed for longer than 15 years are
candidates for replacement. They probably have degraded components and, in many instances,
lack adequate protection against insect infestation. As with most products in contemporary
society, the state of the art of smoke detectors has been greatly enhanced over the past
fifteen years.
Alarm Verification, a feature that can be retrofitted into most control panels by the
panel manufacturer, has been effective in eliminating nuisance alarms from smoke detectors
in many existing installations. It is a technique that is considered valid by Underwriters
Laboratories, who list new panels that contain this feature. Very simply, with alarm
verification an activated smoke detector is "ignored" by the control panel for a
brief period of time. At the end of this short period, the panel revisits the detector and
if it is still activated, the system will alarm.
Alarm verification has proven effective in filtering out false alarms from such transients
as radio frequency interference, electrical disturbances and random tobacco smoke.
Actions to Eliminate Nuisance Alarms from Electrical Disturbances
When fire alarm system circuits leave a building, they need to be protected. Whether
installed overhead or underground, in conduit or direct burial, shielded or unshielded,
fire alarm system wiring outside of buildings on a "campus" needs to be
safeguarded against electrical transients.
Most fire alarm system equipment manufacturers have circuit protection devices
specifically designed for their systems. These devices need to be installed where circuits
leave or enter a building. Protection installed within control equipment is not usually as
effective as protection installed remotely. Once high electrical energy enters control
equipment, it is usually too late to avoid equipment damage and nuisance alarms.
Except in locations that are particularly prone to lightning strikes, it is not usually
necessary to protect the power source to the fire alarm equipment over and above the
standard "on-board" protection. If surges or spikes on the power line are
creating nuisance alarms, the equipment manufacturer can provide guidance on additional
transient protection. If a lightning strike is powerful enough or close enough, it can
cause a nuisance alarm, regardless of the protection. However, by observing these
procedures, nuisance alarms should be very minimal.
The Importance of a Sound Connection to Ground to Avoid Nuisance Alarms
If the energy from a lightning strike or other electrical disturbance is to be kept out of
the fire alarm control equipment, it needs some other place to go; that place is earth or
ground. A good rule of thumb is that the control equipment and all circuit protection
devices should be connected to the same ground as the telephone or electrical service with
a #10 or larger wire.
Dealing with Mischievous Nuisance Alarms from Manual Fire Alarm Pull Boxes
A transparent cover assembly with a battery and a horn is available to fit over a manual
fire alarm pull box. The horn sounds when the cover is lifted to gain access to the fire
alarm box. This cover, which can be mounted over most existing pull boxes, has proven to
be an effective deterrent to nuisance alarms in many installations. Also, relocating a
manual pull box (which has been a source of false alarms) to a location where it can be
more closely supervised should be considered.
Some older designs of pull boxes contained a mercury switch which could be vibrated into
alarm by a sharp blow to the box. This type of vandalism is particularly hard to detect
because the box gives no appearance of having been operated. If alarms are occurring for
no known cause, consider replacing boxes having mercury switches with boxes having snap
action switches.
Dealing with mischievous nuisance alarms from locations such as college dormitories
requires very active involvement by the AHJ.
In some instances, evacuating a building after an alarm and keeping the building
unoccupied for several hours while "investigating the cause of the alarm" will
motivate the residents to police other residents to prevent future nuisance alarms. In
some situations, school officials have imposed fines on every building occupant to
encourage self policing.
Nuisance Alarms from Rate of Rise Heat Detectors
If rate of rise heat detectors are installed in locations where there are wide temperature
variations under normal conditions, they can be a cause of nuisance alarms. Because rate
of rise heat detectors are self restoring, identifying them as the source of an alarm can
be difficult. Locations where the use of rate of rise detectors should be avoided include:
over ovens in kitchens, in front of fire places, over janitor's sinks, in outside
entranceways or near hot air registers.
If a rate of rise detector cannot be relocated away from the source of fluctuating
temperatures, replace it with a fixed temperature heat detector. Because most fixed
temperature detectors are listed to protect smaller spaces than rate of rise detectors,
additional fixed temperature detectors may be required.
Nuisance Alarms from Automatic Fire Sprinkler Systems
Flow switches that connect sprinkler systems to fire alarm systems contain a retard device
to prevent surges and hammers in the water lines from causing nuisance alarms. The retard
mechanism requires a sustained flow of water (from an open sprinkler head) before the
switch will initiate an alarm. A delay that is too brief for the surges present in a
system can cause nuisance alarms. This is another problem that can be difficult to
identify because flow switches are self restoring. Retard times should be adjusted for a
minimum of 45 seconds to avoid nuisance alarms.
The Need for Accurate Records
It is easy to understand why a fire fighter responding to, what turns out to be a nuisance
alarm at 3:00 a.m., is not enthusiastic about identifying the exact smoke detector or heat
detector that initiated the alarm, yet, knowing which device was responsible is critical
if the problem is to solved.
The AHJ needs to obtain the cooperation of the responding fire companies to assure that
accurate records are kept, including the actual device in alarm as well as the time of the
alarm. A log at the protected property as well as a log at fire headquarters is
recommended.
A Step by Step Procedure AHJs Can Pursue to Significantly Reduce Nuisance Fire Alarms
1. Identify the ten fire alarm systems in your jurisdiction that are responsible for the
highest number of nuisance alarms. By looking at the fire alarm control panel, determine
what companies supplied the systems.
2. Schedule a meeting with the suppliers of these ten most troublesome systems. Advise
these suppliers that it is incumbent upon them and you to fix the nuisance alarm problem,
because it is being used as a reason to eliminate fire alarm from the building and life
safety codes. Give them hard data on the ten problem systems. Provide as much information
as possible, including the number of alarms, times of alarms, respected reasons, etc.
3. Require the systems suppliers to perform a walk-through of each of the ten buildings
where the troublesome systems are installed. If possible, assign one of your staff members
to go on each walk-through. Require a written report from the suppliers for each system.
4. Formally notify the owners of the ten buildings that the system supplier will be
performing a survey. Advise the owners of the problem and encourage their support. Repairs
to the troublesome systems should not be expensive, but there will be some cost owners.
5. Consider enacting a law or ordinance that imposes a fine on building owners for false
fire alarms. The fine can be waived or suspended when the building owner takes documented
action to actually fix the problem. (The purpose of the fine is not to generate revenue;
the purpose is to leverage system repairs.)
6. After the ten most troublesome systems have been rectified, start on the next ten. The
fire alarm industry is ready and willing to support your efforts to resolve any nuisance
alarm problems you may have. If you need help contact either of the two major industry
trade groups:
Signaling, Protection and Communications Section
National Electrical Manufacturers Association (NEMA)
1300 North 17th Street, Suite 1847
Rosslyn, Virginia 22209
703 841-3200
Automatic Fire Alarm Association (AFAA)
P.O. Box 951807
Lake Mary, Florida 32795-1807
407 322-6288
This article draws heavily from the booklet "Quality Control of Automatic Fire
Detection and Alarm System Installations" which was prepared by NEMA, AFAA the
International Association of Fire Chiefs and Operation Life Safety. The booklet includes a
model nuisance alarm ordinance as discussed in the article.
The booklet is available from:
Operation Life Safety Resource Center
4025 FairRidge Drive
Fairfax, Virginia 22033-2868
703 273-0911
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