What you need to know about school fire protection systems:
We don’t often read about fires in our K–12 schools, but as recently as two years ago in a Massachusetts city, a fire occurred in a middle school; reportedly, the firefighters were already responding to the 5:22 am municipal master box alarm when a passerby called 911 to report the fire. The four-story, wood and brick building had a pitched roof covered with slate tiles. It also had a complete smoke and heat detection system connected to the municipal fire alarm system. Even though the building did not have sprinklers, fire officials considered it a save. (For more information on municipal fire alarm systems, see National Fire Protection Association’s National Fire Alarm Code, 72-2007, Chapter 9.)
The fire started in a second-floor computer classroom and was brought under control in just a few hours. The $500,000 property damage was limited to the room of origin, and the limited damage can be attributed to the alarm system detecting the fire early and the rapid, efficient response of the fire department.
Early warning and detection
The lessons learned from this fire point to the need for properly designed, complete coverage automatic fire alarm systems in all of our children’s schools whether they are new or existing buildings.
In most of the new schools in the United States, the building code will require an automatic sprinkler system. In our existing school buildings, the chances of a sprinkler system being present is less likely, and then it becomes more important for fire alarm system designers to ensure complete detection coverage throughout the school. Total or complete coverage is defined in NFPA 72-2007 in Section 5.5.2, “Detector Coverage” specifically in section 188.8.131.52, which states, “Total coverage shall include all rooms, halls, storage areas, basements, attics, lofts, spaces above suspended ceilings, and other subdivisions and accessible spaces as well as the inside of all closets, elevator shafts, enclosed stairways, dumbwaiter shafts and chutes.”
The code, as illustrated above, did not specify smoke detection or heat detection. In the fire report outlined at the beginning of this article, it is obvious that the school had what would be considered a typical design. Heat detectors were placed in each classroom with smoke detection in the common halls and stairwells.
When school authorities request a designer to develop a fire alarm system, one of the classic mistakes is the assumption that only hallway smoke detection is necessary to address life safety concerns. Typically, this smoke detection is considered early warning only for the duration the school is occupied. The designer or contractor should make every effort to convince school authorities to install a total coverage fire alarm system using both smoke and heat detection appropriate for the area being covered.
The retrofit issues are characteristically those of access to areas above the ceiling where wiring may be concealed or the building construction makes it difficult to access each classroom. In some cases, school officials will resist the installation of raceway on the ceilings or walls because of aesthetics. Understandably, these issues must be overcome in order to provide the appropriate fire alarm system for the building.
Once the decision to design the system is made, other issues will surface such as false alarm prevention, ease of fire drills and protection of the installed from vandalism, audibility of the alarm signals and delayed response.
False alarm prevention in schools can be addressed in a number of ways. First, the system designer must consider the environment and the type of detector used in each area of the building. For instance, it makes no sense to require smoke detectors in a woodworking shop or a rate-of-rise heat detector in a shower/locker room. It also is important to use weatherproof devices in all areas like a shower/locker room to avoid false alarms from water buildup inside a detector. Once the designer has confirmed there will be no false alarms from poor location or application of detectors, a careful review of all manual fire alarm box locations must be made to determine where the pull station protector should be installed over the manual station.
These protection devices are not connected to a fire alarm system but have a built-in horn and switch mechanism to cause a local alarm when the cover is lifted up to gain access to the manual fire alarm box. The local alarm alerts a teacher or other member of the school staff that someone is attempting to activate the fire alarm system. After a number of students are caught attempting to actuate a manual fire alarm, the number of false alarms will decrease dramatically as long as proper disciplinary action is followed. Of course, the other option could be to eliminate certain manual fire alarm boxes that are in locations normally susceptible to pranksters, such as the restrooms or an exit out of sight of faculty or staff members.
Fire drills are required in most schools to develop a proper response by the students for a safe evacuation. The fire alarm system should be designed to allow the principal an easy method to conduct drills for compliance with local requirements and ordinances. Many of the devices and appliances installed in the school will be installed in areas where physical protection will be necessary. There are many physical protection devices available for heat detectors, smoke detectors and notification appliances. NFPA 72-2007, National Fire Alarm Code, requires listing with the device or appliance when mechanical guards are used with detection devices or notification appliances.
Audibility of the signal in a fire alarm system design is as important as having the correct types of detectors and the proper detection coverage in the building.
Obviously, the ability of the students to hear an alarm signal will depend on where they are in the building and the ambient noise level in the space they are occupying.
Notifying students sitting in the gym watching a basketball game will be more of a challenge than a quiet classroom.
Be aware of the audibility requirements in NFPA 72-2007, which states in section 7.4.2 for public mode signaling, “To ensure that audible public mode signals are clearly heard ... they shall have a sound level at least 15 dB above the average ambient sound level or 5 dB above the maximum sound level having a duration of at least 60 seconds, whichever is greater, measured 1.5 m (5 feet) above the floor in the area required to be served by the system using the A-weighted scale (dBA).” Because this signal is measurable, the professional contractor will need to own a sound level meter to ensure a code-compliant installation.
There may be occasions when school officials will ask the contractor to program the fire alarm control unit to delay the alarm. This is not a good idea and is usually an ill-conceived plan based on false alarm issues. As a point of reference, in every large loss of life or property loss fire in this country, a delayed alarm (either to the occupants or to the fire department) was one of the leading contributing factors to the loss. To avoid costly mistakes or increased liability, the professional contractor needs to ensure he or she has a thorough understanding of the National Fire Alarm Code as it applies to installed fire alarm systems in schools before entering into this market.
MOORE, a licensed fire protection engineer, frequent speaker and an expert in the life safety field, is a co-editor of the current National Fire Alarm Code Handbook. Moore is a principal with Hughes Associates Inc. and is located at the Warwick, R.I., office.