Chapter 2: Smoke control system hardware 
VM-1 Smoke Management Application Guide  35 
Dual duct HVAC systems 
Dual duct HVAC systems provide a central source of 
conditioned air through a hot supply duct and a cold 
supply duct serving multiple zones. Each zone has 
mixing boxes to control room temperatures. 
Configuring for smoke control of dual duct HVAC 
systems utilizes mixing box air flows for pressurization. 
Cold air ducts are often relied upon for air supply due to 
their larger size. 
See Table 6 below for control settings. 
Multi-zone HVAC systems 
Multi-zone HVAC systems provide separate air mixes for 
each HVAC zone with multi-zone units. 
Most systems are limited to about 12 zones due to 
energy efficiency considerations. 
For smoke control, multi-zone systems maximize air to 
zones designated for pressurization around the fire. 
Cold air ducts are often relied upon for air supply due to 
their larger size. 
See Table 7 below for control settings. 
Variable air volume systems (VAV) 
VAV systems serve multiple building zones with 
conditioned air at required volumes. 
Terminal units in each building zone contain dampers to 
control air volume and may contain fans and heating 
coils. 
Damper positioning and controlling of supply and return 
fans to provide maximum air volume are needed for 
smoke control applications using VAV systems. 
Static pressure controls must be reset to permit 
maximum air flow without duct collapse or rupture. 
See Table 8 on page 36 for control settings. 
 
Table 6: Dual duct smoke control settings 
  Adjacent zones  Dual duct central system  Remote zones on same dual duct system 
  Supply fan ON   
  Return fan ON   
  Exhaust air damper CLOSED  Exhaust air damper OPEN  Exhaust air damper CLOSED 
  Exhaust air damper CLOSED  Outside air damper OPEN  Hot duct damper CLOSED 
duct damper CLOSED  Hot duct damper CLOSED  Return air damper CLOSED  Cold duct damper CLOSED 
Cold duct damper CLOSED  Reset static pressure control to 
maximize air flow and prevent duct 
failure 
 
 
Table 7: Multi-zone smoke control settings 
  Adjacent zones  Multi-zone central system  Remote zones on same multi-zone system
  Supply fan ON   
  Return fan ON   
  Exhaust air damper CLOSED  Exhaust air damper OPEN  Exhaust air damper CLOSED 
 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