Introduction; Design Parameters; Design Concepts - Simplex 4100U Application Manual

Introduction

Design Parameters

Design Concepts

A smoke control system can be designed to provide an escape route and/or safe zone.
However, all smoke control systems have the following design parameters:
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Air-flow paths through a building and leakage areas.
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Pressure differences across smoke control system boundaries.
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Door or vent openings in the boundary of a smoke control system.
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Airflow through openings in smoke control system boundaries.
The following factors can affect the design of a smoke control system:
System Flexibility:
System flexibility means using features that allow for easy adjustment of a particular system to
meet the demands of a given situation. For example, during the design and construction of a
building, leakage paths can be estimated. Thus, a smoke control system can only be designed to
provide theoretical protection from smoke. After the building is completed, the system must be
tuned to the actual pressure values. System flexibility is also useful when retrofitting smoke
control systems in existing buildings.
System Control:
A smoke control system should be designed to automatically activate, preferably by an alarm from
a smoke detection system in the fire zone. The advantage of this type of activation is that the
system is activated in the earliest stages of a fire. Smoke control systems should be activated after
the receipt of alarms from a properly designed smoke detection system.
Energy Conservation Management:
Energy conservation methods must be considered when designing a smoke control system.
A smoke control system must be designed to override the local heating, ventilation, and air
conditioning (HVAC) system, or energy management system in order to implement the desired
smoke control operations.
Use of Fire Suppression Systems:
Many fire protection schemes use automatic fire suppression systems. However, while the
functions of fire suppression and smoke control are both desirable, they are not intended to
substitute for each other.
Fire suppression systems are intended to limit the growth rate of a fire. Smoke control systems can
provide safe zones and tolerable conditions along exit routes, but can do little to control fire. In
addition to the obvious differences between the two systems, the way the systems interact must be
considered. For example, pressure differences and air flows are different in the various buildings
within a complex that is protected by a fire suppression system. A water spray from a sprinkler
might interfere with air flow to a smoke exhaust or an outside air pressure system or a smoke
control system could interfere with the performance of a gaseous agent (e.g., Carbon Dioxide or
Nitrogen) fire suppression system.
A general guideline is that the gaseous agent fire suppression system takes precedence over the
smoke control system. It is also desirable that the smoke control system be able to purge the
residual gases and smoke after the fire is extinguished, and replace them with fresh air. This is an
important life-safety consideration, since some fire-suppression gases are asphyxiates.
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