Design Dynamics

Building use dictates fire and life safety dimensions

• By David George
• Apr 21, 2008

A comprehensive fire and life safety design requires a cohesive blend of alarm and detection capabilities, an appropriate suppression system and a number of other building construction features related to occupancy, facility type and use of space. Planning, an often overlooked component, is integral to keeping occupants safe.

In a building such as an apartment complex, the alarm and detection system is critical because occupants may need to be awakened. Alarm and detection features can provide early warning for occupants, fire department notification and the ability to unlock doors through a panel. In large public venues, shopping malls or arenas, the notification systems may integrate voice communication to give emergency instruction to those who are not familiar with the building layout and design. Suppression becomes the focus of the system for healthcare occupancies, correctional facilities, high-rise buildings or other places where evacuation would cause considerable disturbance.

Weighing the Options
“An automatic fire sprinkler system has the ability to control the situation, thereby limiting the effects of the fire. This allows additional time for occupants to move to a safe area,” said Robert E. Solomon, P.E., National Fire Protection Association. “Of course, the presence of a well-thought-out means of egress, with adequate exits, stairs and doors, also is crucially important.”

The means of egress also should be thought of as a system that takes into consideration the number, type and arrangement of the egress components.

Some construction options may require the integration of firewalls, fire barrier walls and smoke compartments, as well as protection schemes for vertical openings between floors.

“There are interior finish criteria defined for floor, wall and ceiling coverings,” Solomon said. “These features can be specified to the desired level of fire resistance. Fire resistance is usually measured in hours for a firewall, based on the building’s structural system. Fire resistance also is measured by flame spread and smoke-developed characteristics for an interior wall finish. The level of fire safety performance intended for the building is contingent upon its use.”

Space Use
NFPA codes, such as NFPA 101, Life Safety Code, and NFPA 5000, Building Construction and Safety Code, provide occupancy-specific requirements depending on the use of the building or parts of the building. The codes set standards based on the overall characteristics of the occupants that could affect their egress time from the building.

Most code provisions for business occupancy presume that the majority of occupants are familiar with the building and the environment, are awake and alert, and are capable of self-preservation through actions to evacuate from the area.

“In a healthcare occupancy, the code applies an approach that strives to minimize the need to relocate, and certainly to evacuate, the patients,” Solomon said. “In this case, the occupants who are patients are largely incapable of self-preservation. The hospital staff play crucial roles in protecting patients. Their role is supported by the construction, compartmentalization, fire alarm system and sprinkler system features of the structure. Assistance from others is absolutely critical to protect patients with limited mobility.

“In educational facilities, a fairly broad mix of construction and building systems protects the students. Evacuation drills are important to keep the students safe. Hopefully, school-aged children will retain the importance of the drills into their adult lives.”

Code provisions for hotels, dorms and apartment buildings use additional fire alarm components, specifically smoke alarms and detectors. In residential environments, occupants may be sleeping, increasing the importance of automatic fire detection for early warning.

Regardless of the type of facility, the presence and composition of combustible materials warrant some added protection features, such as fire-rated walls and self-closing fire doors. Large conference rooms and cafeterias that hold more than 50 people need to adhere to the supplemental rules for assembly occupancies. In addition, interior finish regulations are more restrictive in egress corridors than in individual work spaces or rooms accessible through these corridors.

Another Dimension
Carbon monoxide detection in a monitored system adds another life safety dimension to the overarching plan. CO is an odorless, tasteless gas that is known as a silent killer. Incorporating CO detection and monitoring into life safety systems and plans can prevent or minimize hazards. Public officials, as well as citizens, prefer to take a proactive approach.

Massachusetts recognized the importance of CO detection and passed Nicole’s Law to safeguard its residents. The law requires CO detectors for all residential occupancies, including single-family homes and attached garages, that use fossil-burning fuels such as oil, gas, coal or wood. It also restricts a property from being sold or transferred without having a CO detector or system in place.

CO detectors have been available for several years, and the technology has been refined. NFPA 720, Standard for the Installation of Carbon Monoxide Warning Equipment in Dwelling Units, is being updated to reflect best-practice installation methods and equipment features. The UL product standard ANSI/UL-2034, Standard for Single and Multiple Station Carbon Monoxide Alarms, also has been revised.

There are three main power sources for CO detectors. The first, a battery-powered detector, requires annual battery replacement. When the battery reaches the end of its lifespan, the detector will chirp to alert homeowners. The second, a 120-volt detector, runs off the building’s main power supply. The third, a system-connected 12-/24-volt device, can be wired to a security or fire panel. This type of system offers monitoring by a central station to provide extra protection if the residence is empty, if the residents are sleeping or if they are already suffering the effects of CO poisoning.

Each type of detector offers the ability to connect CO detectors to a control panel to monitor and automatically summon help in an emergency.