Chapter 2: Smoke control system hardware
34 VM-1 Smoke Management Application Guide
Central HVAC systems
Central HVAC systems are most often used in multiple
floor buildings with a single HVAC system providing
service for 6 to 20 floors.
Conditioned air is supplied to each floor via large vertical
shafts with each HVAC zone having reheat provisions.
Damper positioning is the key component in isolating
smoke control zones in these systems.
Control of static pressures in large vertical shafts
supplying or exhausting air is necessary to prevent duct
collapse or rupture during smoke control events.
See Table 5 below for control settings.
Table 3: Single zone smoke control settings with direct outside air and direct exhaust air
Adjacent zones Remote zones
Supply fan ON
Maintain HVAC operation while power supply is
available without impacting fire area smoke
control operations
Return fan OFF
Exhaust air damper CLOSED
Return air damper CLOSED
Outside air damper CLOSED
Outside air damper OPEN
Reset static pressure control to maximize air
flow and prevent duct failure
Reset static pressure control to maximize air
flow and prevent duct failure
Table 4: Single zone smoke control settings with common outside air and exhaust ducts
Adjacent zones Common outside and exhaust air system Common remote zones
Supply fan ON Supply fan ON* Supply fan OFF
Return fan OFF* Return fan ON* Return fan OFF*
Exhaust air damper CLOSED Exhaust air damper OPEN Exhaust air damper CLOSED
Supply air damper OPEN Outside air damper OPEN Supply air damper CLOSED
Return air damper CLOSED Reset static pressure control to maximize air
flow and prevent duct failure
* If no return fan is present, dampers are still
positioned as indicated.
Table 5: Central system smoke control settings
Adjacent zones Central system Remote zones on central system
Supply fan ON
Return fan ON
Exhaust air damper CLOSED Exhaust air damper OPEN Exhaust air damper CLOSED
Supply air damper OPEN Outside air damper OPEN Supply air damper CLOSED
Return air damper CLOSED
Reset static pressure control to
maximize air flow and prevent duct
failure
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