What essential safety action should a Fire Alarm Control Panel (FACP) automatically initiate for a building's HVAC system upon a confirmed fire alarm activation?

Upon a confirmed fire alarm activation, the Fire Alarm Control Panel (FACP) automatically initiates the essential safety action of controlling the building's Heating, Ventilation, and Air Conditioning (HVAC) system to manage fire and smoke hazards. The FACP, which is the central control unit of a fire alarm system that monitors inputs and controls outputs, sends signals to the HVAC system components. A confirmed fire alarm activation occurs when the FACP processes multiple inputs, such as from smoke detectors, to verify a fire event is highly probable. The primary control action is typically to shut down general air movement fans and automatically close associated smoke dampers and fire dampers. Smoke dampers are devices within ductwork that close automatically to restrict the passage of smoke, while fire dampers do the same for fire. This shutdown is critical to prevent smoke spread, which is the rapid movement of smoke, hot gases, and toxic combustion products throughout a building via air currents and ventilation systems, and to limit the oxygen supply to the fire, which is the provision of oxygen necessary for combustion that HVAC systems can distribute. In buildings equipped with engineered smoke control systems, which are designed to actively manage smoke movement during a fire, the FACP instead places specific HVAC components into a pre-programmed smoke control operating mode. This mode uses dedicated fans and dampers to create pressure differentials, such as pressurizing stairwells or exhausting smoke from fire zones, to contain or exhaust smoke rather than a full shutdown of all air movement, thereby maintaining tenable conditions and assisting emergency responders.