Protecting Protective Devices

04/01/2006


Today's building codes require fire-alarm systems for all types of occupancy classifications, including those that present conditions that are potentially hostile to the equipment.

In these "high-risk" occupancies, which can include correctional and detention facilities, rehabilitation centers, prerelease centers and even schools, fire and life-safety systems must be protected from vandalism and tampering that can result in the interruption of operations and endanger the occupants themselves.

The International Building Code (IBC), 2003 Edition, Section 907 and the Life Safety Code (NFPA 101) require that a manual, automatic or combination manual/automatic fire-alarm system be installed within potentially hostile facility types. Manual fire-alarm systems consist of manual stations, while automatic fire-alarm systems consist of smoke detectors, heat detectors, sprinkler alarms or any other type of initiating device that automatically activates in the presence of smoke or fire. In addition to the activation requirements, fire-alarm systems may also be required to monitor and/or control additional life-safety functions such as smoke-control, special suppression and security systems.

Fire-alarm devices, such as initiation devices and notification appliances, when vandalized, are not only expensive to repair or replace but also present a variety of life-safety hazards. If fire-alarm devices are damaged, the detection of a fire will be hindered, and building occupants may not be notified of an emergency within a reasonable time. Damage to or removal of fire-alarm devices within correctional facilities and rehabilitation centers present an even greater concern with life safety. Similar to hospitals, many of the life-safety elements within these facilities utilize a "defend or protect-in-place" strategy, which allows the quick extinguishment of a fire without the need to evacuate the occupants. Within high-risk facilities, occupants may be in a locked-down environment and cannot be evacuated into a public space or to the outside.

The fire-alarm systems within correctional and rehabilitation facilities are often designed to provide a positive sequence alarm. NFPA 72 defines a positive sequence alarm as "an automatic sequence that results in an alarm signal, even when manually delayed for investigation, unless the system is reset."

This sequence will allow security personnel to acknowledge an alarm condition within a maximum of 15 seconds, investigate the alarm within a maximum of three minutes and determine if the system should be reset or be allowed to activate the emergency sequence.

Protective covers for manual stations

Protective covers are often utilized in schools and hospitals in order to help prevent nuisance alarms. These covers encase manual stations and must be lifted in order to activate them. Many protective covers also contain local alarms that trigger when the cover is lifted a certain distance. This cover still allows occupants to activate the manual station during a real fire emergency but helps prevent prank alarms by requiring an extra step to activate the alarm.

Institutional manual stations go a step further by requiring a special key to activate the fire-alarm system. This type of station is only permitted in certain occupancy types such as correctional and detention facilities and is required to be located in accordance with IBC Section 907.3 and NFPA 101 Section 9.6.2. Security or designated personnel must be present at all times and must have access to the manual station key in order to provide quick activation of the system.

While institutional manual stations and protective covers prevent or at least discourage accidental or intentional fire-alarm activations, they still might not completely protect the device from vandalism.

Out of the "danger zone"

As discussed earlier, manual stations in hostile locations are required to be located in accordance with IBC Section 907.3 and NFPA 101 Section 9.6.2. While these requirements are similar to those for most occupancy types, there is an exception for facilities that contain constantly monitored areas such as resistant housing. Manual stations can be omitted from the fire-alarm design at these normally required locations but must be provided in staff-attended locations having direct supervision over these areas.

Of course, omission of manual stations from these areas protects them from vandalism and allows only direct access by designated personnel. While this approach seems most feasible, careful consideration should be taken with where to locate stations. Constantly staff-attended locations, often known as control rooms, should be carefully examined so that the manual stations are located in an obvious location that is easily accessible. Manual stations should be distinct from other security or control functions within the control rooms so that if a real fire event occurs, there are no delays in the activation of the fire-alarm system.

Automatic initiation device locations

IBC and NFPA 101 require the use of automatic detection and/or fire-suppression systems in most of the previously mentioned facility types. Since many of them use the protect-in-place strategy, early-warning protection and suppression systems are needed to detect a fire and contain it to the room of origin. In order to accomplish this level of protection, facilities are often required to have complete detection coverage. This equates to detection devices within areas that are more prone to vandalism such as inmate cells or any area where occupants may be present.

Protective coverings for smoke and heat detectors are designed to protect the devices from tampering or vandalism without delaying detection of smoke or fire. These devices consist of steel wire meshing secured to a wall or ceiling with tamper-resistant screws. The wire mesh configuration and size should be unique to the device being protected. Coverings specifically designed for smoke detectors must not be used with heat detectors since the design may delay the passage of heat to the device. Consideration should also be taken for the location of devices and coverings. If possible, they should be located out of the reach of occupants, which helps keep the protective mesh from being clogged with items such as toothpaste or paper. In addition, since the protective coverings may protrude from the wall or ceiling, they should be secured in such a way that occupants couldn't wrap items around or hang items from them in order to harm themselves.

The good news for the detection devices is that the IBC and NFPA 101 permit them to be located in exhaust ducts in most institutional facilities, making them inaccessible to occupants and preventing vandalism and tampering. When locating these devices in exhaust ducts, consideration must be taken regarding the configuration of the exhaust system, location of the exhaust grills and the potential "lag time" for heat and smoke to reach the devices.

Air-sampling detection

Air-sampling detection is one of the newest technologies for providing smoke detection without the use of smoke detectors. Air-sampling detection systems consist of capillary tubing and detection ports strategically located to provide complete coverage of the area(s) protected. The tubing leads back to a detection panel, which constantly monitors the air quality to detect the presence of smoke. The detection ports can be located within exhaust ducts or within the wall and ceiling structure, allowing for the elimination of larger smoke detectors and for "hiding" equipment from the occupants.

While this type of detection system is feasible for new facilities, this might not be the case for retrofits, as the routing of the capillary tubing may be difficult in existing facilities due to the original structural layout.

Performance-based design

While building and fire codes specify prescriptive design minimum requirements for all types of facilities and occupancy types, they also allow for performance-based design approaches, provided these are reviewed and approved by the authority having jurisdiction (AHJ). Performance-based designs make unique alternative design approaches possible through establishing performance criteria, conducting analyses and testing. NFPA 72 Annex B is one of many engineering guides for performance-based design, as it provides a procedure for determining detector spacing and fire-alarm performance through calculations of fire growth, environmental and ceiling temperatures and detector-response characteristics.

As discussed earlier, vandalism and tampering are a major concern in facilities that are characterized by potentially hostile conditions. By designing a system through performance analysis and testing that is unique to the facility, the number and location of the detectors could be reduced significantly, thus reducing this threat. Live fire tests, fire modeling programs and detector performance analyses are some design approaches that can be taken to reduce the number of detectors needed while at the same time maintaining an adequate level of life safety.

More than one option

Different design measures can be taken to protect fire-alarm system from vandalism, tampering or nuisance alarms, and there are many vandal-resistant protective devices commercially available. Keep in mind that these devices should be carefully analyzed with the proposed fire-alarm system design and facilities configuration, and both the equipment and design should always be discussed with the AHJ.



Improved Smoke Ventilation at Atlanta's Airport

When the city of Atlanta finalized plans for the capital-improvement project at Hartsfield-Jackson Atlanta International Airport, an integral part of the 10-year, $5.4 billion project included upgrading the ventilation system of the expanded automated people mover (APM) to meet National Fire Protection Assn. standards for emergency smoke evacuation.

The city of Atlanta, owner of the airport, initiated the Hartsfield Development Program (HDP) in 2000 to enable the airport to meet future demand, a projected 121 million passengers annually by 2015. The airport currently serves more than 80 million passengers annually. Improvements underway include construction of a fifth runway, an additional concourse and a four-gate expansion of Concourse E, which handles international operations.

A three-story underground substructure houses the APM train system and its maintenance facility and connects all concourses with the terminal. The ventilation system was retrofitted with four six-ft. diameter 125-hp reversible vane-axial fans capable of venting/exhausting the tunnel at 120,000 cu. ft. of air per min. Four 125-hp drives control the fans. A digital controller and backup controller are located at each of the two tunnel entrances to monitor temperature and detect fire/smoke.

"The fans are strictly there for fire emergencies, with a secondary task of providing ventilation, as the trains generate a lot of heat, especially when the outdoor temperature is higher," says Sam Green, vice president and project manager, W.B. Wallis & Co., Atlanta, the project's M/E contractor. "The fans are placed at either end of the tunnel—two in the underground maintenance facility and two on the rooftop—so that in case of emergency, one fan can extract smoke and another can blow in clean air."

To provide ventilation in the tunnels, one fan at each end runs for a seven-day time period, then alternates with the second fan to equalize wear. The fans run at speeds of 30% to 70%, depending on the heat generated in the tunnel. In a fire or smoke situation, the fans ramp up to full speed.

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