What is staircase pressurisation

Where a smoke-free lobby is also pressurised, the pressure at the exit staircase shall always be higher. Where the smoke-stop lobby is pressurised, the pressure gradient shall be such that the pressure at the exit staircase is always higher. The force required to open any door against the combined resistance of the pressurising air and the automatic door closing mechanism shall not exceed N at the door handle.

Measurement of the force required to open a stair door can be simply carried out by using a force-measuring in the push or pull mode e. The maximum force permitted to open a door in accordance with this Code is N. This equates to a force of Lever operated latch sets are probably the easiest to measure. To take a reading, slowly and steadily pull the spring balance and read the scale as the door just starts to open.

Air flow velocity of at least 1. The air flow velocity measurement through an open door of a pressurised staircase is taken from the entrance of any of two successive doors held open together with its exiting door at the 1st storey. This air flow must be maintained across the doorway providing egress from the fire-affected storey into the staircase during a fire.

Initially, building occupants from both the fire floor and the floor above the fire floor will evacuate the building and, depending on the fire situation, this may be simultaneous operation.

The requirement for two floor doors and the 1st storey door opening into the exterior to be open the same time has two applications:. Initially hose will be run from the floor below up the staircase and onto the fire floor hence a minimum opening of two doors is involved. Thus the final exit door would remain in the open position at all times.

When in operation, the pressurisation system shall maintain an airflow of sufficient velocity through open doors to prevent smoke from entering into the pressurised area. The flow velocity shall be attained when a combination of two doors from any two successive storeys and the main discharge door are fully open.

The velocity averaged over the full area of each door opening shall not be less than 1. Pressurised air could leak through areas such as gaps around doors, windows, other ventilation openings and other places where air will escape. To avoid a pressure built-up in the occupancy area, adequate measures shall be taken to allow air leakage, e.

A pressure build-up would create difficulty in opening the doors to the occupancy area. The rate of supply of pressurised air to the pressurised areas shall be sufficient to make up for loss through leakages into the unpressurised surroundings.

Adequate relief of leaked air out of the occupied area shall be provided to avoid a pressure build-up in this area. The relief can be in the form of perimeter leakages or purpose built extraction systems. The above installation is not acceptable as over pressurisation would occur at the upper portion of the staircase. Supply air to the staircase should be well distributed by a vertical supply duct, preferably serving all the levels of the staircase.

An example of an arrangement showing good distribution of supply air can be seen in Figure 7. The number and distribution of injection points for supply of pressurising air to the exit staircase should ensure an even pressure profile complying with Cl.

A dedicated smoke control system is installed in a building for the sole purpose of controlling smoke. It is a separate system of air moving and distribution equipment that does not function under normal building operating conditions. Dedicated systems are used for special areas, such as elevator shafts and stair towers that require special smoke control techniques. Non-dedicated smoke control systems are systems that share components with some other systems such as the building automation HVAC system.

When activated, the system changes its mode of operation to achieve the smoke control objectives. Categories Building maintenance , Emergency procedures , Escape routes ,. Size of site Large , Very Large ,. Level of Best Practice Innovative ,. Considerate Constructors Scheme www. The Scheme does not promote or endorse any products, goods or services. For more information, click here. The Hub features examples of construction industry best practice sourced from across the UK and Ireland.

It can be used by anyone in the industry including site managers, contractors, suppliers and clients, who are looking to improve their standards of considerate construction.

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