SMOKE CONTROL SYSTEMS
Smoke control systems (or smoke management systems) are mechanical systems that control the movement of smoke during a fire. Most are intended to protect occupants while they are evacuating or being sheltered in place. The most common systems referenced in current codes are atrium smoke exhaust systems and stair-pressurization systems. In some specialized cases, zoned smoke control systems may be provided. These feature zones or floors that are either pressurized or exhausted to keep smoke from spreading.
The IBC contains mandatory provisions for smoke control systems. Designers can find NFPA’s detailed provisions in two non-mandatory documents, the Recommended Practice for Smoke Control Systems (NFPA 92A) and the Guide for Smoke Management Systems in Malls, Atria, and Large Areas (NFPA 92B).
The manual controls required or provided for smoke control systems are a primary consideration for the fire service. These manual controls can override automatic controls that activate these systems. When fire department personnel arrive, they can assess whether the automatic modes are functioning as intended. Incident commanders may then use the manual controls to select a different mode or turn any given zone off. It is imperative that these controls override any other manual or automatic controls at any other location.
A simple, straightforward control panel with manual switches for the smoke control system(s) will assist a firefighter who may be trying to decipher how the controls work just after awakening in the middle of the night. Also, similar to annunciators, the fire department may have specific requirements or recommendations, and may prefer uniformity of panels within their jurisdiction.
Both the IBC and NFPA 92A call for status indicators for each fan, damper, and other device. The ICC requires individual controls for each of these devices, but permits them to be combined for complex systems. A system need not be very large to be considered complex.
A good, simple panel layout might feature a single switch for each system or zone (Figure 7.4). Each different position of the switch places the system in a given mode, and the corresponding activation or setting of the individual devices would be configured “behind the scenes.” For example, a stair pressurization system might contain a three-position switch for each of three modes: ‘automatic,” “pressurize,” and “off.”
Zoned smoke control systems are often arranged with each floor as a separate zone. In other cases, a floor may be split into multiple zones. These should be indicated on a graphic display, either on or adjacent to the smoke control panel. See the section, Graphic Displays, on page 53, for additional guidance on graphic displays.
Designers should not confuse smoke control systems with smoke or heat venting systems. The latter are mechanical systems for the removal of smoke. They are often arranged to activate only manually. In some cases, they only remove smoke after an incident.