Passive System: Flexible Fire and Smoke Curtains. Referred to as "passive" because they require no mechanical systems to support them, flexible fire and smoke curtains have been successfully used for elevator fire and smoke protection for some time. But their application for atrium designs, interior stairs and escalators is relatively new in the US. Unlike an active smoke management system that only addresses smoke exhaust or evacuation, a passive system that incorporates fire-rated smoke curtains contains and compartmentalizes fire and smoke before they reach the open area of an atrium. In building applications where fire/smoke protection is of special concern the addition of such a passive system would be clearly advantageous as enhanced protection.

All smoke management systems require commissioning and the services of a fire protection engineer and mechanical engineer to certify proper operation after installation. Compared with a complex active smoke exhaust system, passive curtains are a simpler system and therefore less expensive to certify or commission.

Another appealing feature of the curtains is their invisibility. "We evaluated a number of alternative methods utilizing accordion doors or doors held open on magnets," says project manager B.A. Eastwood of PHA Architects. "Due to aesthetic impacts of doors, closets and tracks, we elected to pursue a roll-down smoke curtain."

As can be seen from their many performance and design benefits listed below, fire and smoke curtains present a productive and energy efficient option to replace or supplement traditional atrium smoke management solutions.

Performance and Design Features of Curtains:

• Controls smoke through passive containment and compartmentalization rather than by an active mechanical system which controls the movement of smoke.
  
  
• Curtains are lightweight and do not require structural re-enforcement for installation.
  
  
• Employ space-saving curtain containment assemblies.
  
  
• Containing the spread of smoke makes it easier for the fire department to locate the fire.
  
  
• As a passive operating system, smoke curtains use less energy than a smoke exhaust system.
  
  
• Available in a wide range of dimensions.
  
  
• Vertical curtains can be equipped with a gravity fail-safe function that allows them to deploy even if power is lost. Horizontal curtains may have either a spring-operated closing device for smaller openings, or a supplemental power source for larger openings.
  
  
• May be selected as the only smoke management system. One curtain can replace a whole smoke exhaust system with its extensive system of vents, dampers and so forth (see Case Study 1).
  
  
• May be selected as a supplement to an exhaust system; they can increase the effectiveness of smoke and heat evacuation.
  
  
• Curtains can subdivide space served by a mechanical smoke exhaust system, thus potentially reducing the initial cost and operating cost of the system (see Case Study 2).
  
  
• Can be configured to channel smoke evacuation so as to provide safe escape routes according to code requirements.
  
  
• Vertical curtains can be rated for smoke leakage.
  
  
• Invisible when not deployed.
  
  
• Less expensive to commission or certify.

Curtain systems should work in conjunction with the other elements of the building's mechanical smoke control systems through a properly designed sequence of operations. An improperly designed sequence of operations can result in damage to some parts of the smoke control system. This is a key feature that design professionals should be aware of.