Smoke Control Systems

Basic Principles

A smoke control system is a system that controls the movement of smoke and air within a building. This system may consist of various components and may use several methods to achieve the design objective. The main goal is usually to maintain a safe (tenable) environment for a sufficient period so that all occupants can safely evacuate the building.

The design objective of a smoke control system may vary depending on the application. For example, in a hospital, the goal may be to contain the smoke within the zone where the fire originated. These systems may be part of existing HVAC systems or installed as separate (independent) systems.

There are several methods of smoke control. Smoke control systems include two types:

• Smoke management systems

• Smoke containment systems

Smoke containment systems prevent smoke from entering certain areas by creating pressure and are typically used in enclosed stairwells.

Smoke management systems, on the other hand, maintain a safe environment in evacuation routes in large-volume spaces or prevent smoke from spreading to adjacent areas. These systems are mainly installed in buildings with multi-story atriums.

Smoke Containment Systems

There are several types of smoke containment systems used for small and enclosed spaces:

• Stairwell pressurization

• Zone smoke control

• Elevator shaft pressurization

• Vestibule pressurization

• Smoke refuge area pressurization

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Most of these systems operate on a similar principle. Pressure is applied to a specific area (such as a stairwell, elevator, vestibule, or building zone) using a mechanical fan. The pressure difference across a barrier prevents smoke from entering that area.

This allows these areas (usually evacuation routes) to remain safe for a longer period, providing occupants with additional time to evacuate and enabling emergency services to operate effectively.

Smoke Management Systems

Smoke management systems used for large spaces such as warehouses or atriums include:

• Mechanical smoke exhaust

• Natural smoke ventilation

Natural ventilation removes smoke by using its tendency to rise, while mechanical smoke exhaust systems use fans to remove smoke and air from the building.

The objective of these systems is typically to maintain the smoke layer interface above the highest usable level of the space for a specified period.

Mechanical smoke exhaust systems must provide a path for make-up air. Otherwise, the pressure may increase to a level that negatively affects other building systems.

For example, the pressure difference across a door should not increase the force required to open it beyond 30 lbf (133 N), otherwise the door may become too heavy for occupants.

It is also important that the make-up air is clean and fresh and not drawn from the area where smoke is being exhausted.

Activation

Both smoke management and smoke containment systems are automatically activated by one or more fire detection devices. These include:

• Sprinkler water flow detectors

• Smoke detectors

• Heat detectors

Manual activation devices should not be used in smoke control systems that are required to determine the location of a fire, because the likelihood of someone manually activating the system in the fire area is low.