Trane BAS-APG001-EN manual Non-compensatedpressurization technique, Smoke control overview

Chapter 1 Smoke control overview

If the technique employs modulated supply airflow, a fan provides at least minimum pressure when all stairwell access doors are open. Either a single-speed fan with modulating bypass dampers or a variable frequency drive varies the flow of air into the stairwell to compensate for pressure changes.

If the technique employs over-pressure relief, a damper or fan relieves air to the outside to maintain constant pressure in the stairwell. The amount of air relieved depends on the air pressure in the stairwell. A barometric damper, a motor-operated damper, or an exhaust fan can be used to maintain the air pressure.

Non-compensated pressurization technique

The non-compensated pressurization technique provides a constant volume of pressurization air. The level of pressurization depends on the state of the stairwell access doors. When access doors open, the pressure in the stairwell lowers. When access doors close, the pressure raises. One or more single-speed fans provide pressurization air (Figure 5).

Non-compensated stairwell pressurization works best when:

•Stairwells are in a lightly populated building (for example: telephone exchanges and luxury apartments).

•Stairwell access doors are usually closed, but when used, remain open only a few seconds.

Figure 5: Sample non-compensated system

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