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Smoke and fire ventilation: Colt pressurisation systems

A pressurisation system protects escape routes and fire-fighting shafts against the ingress of smoke. Smoke and fire ventilation is maintained by the pressure within the escape route being higher than that in the adjacent spaces. They provide no protection within the space containing the fire, but contain the smoke and heat so that it cannot enter the main building escape routes.

Product info

Pressurisation systems offer these benefits:

  • Protection of escape routes
  • Protection of fire-fighting shafts
  • Compliance with Approved Document B and BS EN 12101-6
  • Ideal for multi storey residential apartments.

A pressurisation system consists of three main components: Supply Air (where air is injected into the area that is to be protected), Pressure Relief (to avoid overpressure when doors are closed) and Air Release (air and smoke is released from the adjoining fire area). Combining these elements creates a positive pressure difference which prevents lobbies and staircases from filling up with smoke.

A pressurisation system for smoke and fire ventilation should meet the recommendations of Approved Document B and BS EN 12101-6 "Specification for Pressure Differential Systems" or BS 5588-4 - "Code of practice for smoke control using pressure differentials".

In commercial buildings pressurisation is normally carried through up to the final door to the accommodation, with air release provided from the accommodation. In apartment buildings it is usually impractical to carry pressurisation up to each apartment door due to the difficulty of providing air release from each apartment. Therefore stairs and lobbies are usually pressurised with air release from the corridor.

The System Comprises:

  • Inlet Fans for introducing air into the designated area. The run and standby fans and control equipment should be housed in a separate plant room or outdoors and the inlet should be protected from smoke. Dual inlets with automatic smoke dampers are required for high level inlet.
  • Ductwork and Outlet Grilles, to provide distribution of air exactly where it is needed.
  • Pressure relief dampers, to release excess air in the closed door condition from the stair area. This should be ducted to discharge directly to atmosphere independent of the wind direction. Damper blades are set to start opening at 50 Pa pressure differential.
  • Automatic air release to prevent unwanted pressure build up in the adjacent spaces. This may be automatic vents, natural shafts or mechanical extract systems.
  • The control system should operate automatically from the smoke detection system with a manual on/off switch also provided within either the pressurisation plant room, near the building entrance (to suit fire service), or within the central building services control room.

System Requirements:

There are two requirements to maintain within a pressurisation system. These are:

  • Maintaining a pressure difference for a closed door condition. Here the pressure difference is required to overcome buoyancy pressure generated by the hot smoke layer, expansion of the gases in the compartment due to heating, stack pressure and wind pressure
  • Maintaining a velocity for an open door condition. Here maintaining a velocity for an opened door is required to hold back the smoke on the fire floor when the door onto the fire floor is open.
  • Getting the right balance for a pressurisation system needs careful design in order for the system to work effectively. Insufficient pressure difference across a closed door will allow the passage of smoke into the protected space. Excess pressure will impede door opening and hence escape.

Design Methodology:

  • Assess the usage and layout of the building, the area to be pressurised and the class of system required.
  • Assess the leakage paths (through doors, lifts, vents).
  • Calculate the required volume flow rates.
  • Calculate the area of pressure relief dampers.
  • Calculate the area of air release ventilation.

We can assist with the design of smoke ventilation schemes. We offer a free technical design service on all projects undertaken. Please contact us for further information.

Air Supply System

Stairwell pressurisation system, to class A/B/C/D/E to BS 5588-4:1998 as amended or BS EN 12101-6:2005.

The system shall provide pressurisation to the stairwell only / and lobbies / and lift shaft / , lobbies and lift shaft. Air flow rates shall be calculated assuming tight / average / loose construction of the protected shaft.

The system shall incorporate duty and standby fans with automatic change over, mounted on the roof / in a separate plant room / in a general plant room / at ground level. The fans shall supply air through a duct system to the stairs and lobbies / and lift shaft / , lobbies and lift shaft. Separate duct risers shall be provided for each. Air supply grilles shall be provided every 3 storeys in the stairwell and to every lobby / and to the top / bottom of the lift shaft. Ducts shall be fire resistant where they pass within the building but outside the protected shaft or through a general plant room. Ducts shall otherwise comply with the requirements of DW/144.

Sufficient volume control dampers shall be provided to allow correct balancing and control of overall air flow rate on commissioning.

If the supply air intake is at roof level then two air intakes shall be provided, at least 5m apart and facing onto different elevations. Smoke detection in the duct shall close one intake if it becomes affected by smoke.

Air intakes shall be provided with Colt Seefire ventilators, type LS/ to provide weatherproof closure when the system is not in use.

Overpressure relief in the stairwell shall be provided by a wall or roof mounted pressure relief damper behind a Colt Seefire ventilator, type LS/, to provide weatherproof closure when the system is not in use.

Power to the system shall be provided from a maintained supply and cables shall be fire resistant where they pass outside the protected shaft. The maintained supply (by others) shall terminate at a changeover panel close to the pressurisation system control panel location / terminate at the pressurisation system control panel. All wiring from this point shall be the responsibility of the pressurisation system supplier.

In automatic mode, the system shall be activated by the building fire detection system / a dedicated fire detection system incorporating smoke detectors in the accommodation adjacent to each door into the protected shaft and supplied as part of the pressurisation system.

The control panel or a mimic panel for fire service use shall be mounted in a position accessible to and agreed with the fire service and shall incorporate status indication and manual override for fire service use.

Indication shall be provided for:

  • Power supply available - green
  • Fan 1 run / flow proven - green
  • Fan 2 run / flow proven - green
  • Fan 1 fault - amber
  • Fan 2 fault - amber
  • Air intake 1 open - green
  • Air intake 2 open - green
  • Fire condition - red

Fire override control shall be provided for:

  • Fan 1 - off / auto / run
  • Fan 2 - off / auto / run
  • Air intake 1 - close / auto / open
  • Air intake 2 - close / auto / open

The design shall take account of the available accommodation air release to be provided by:

  • Building leakage
  • Automatic opening ventilators
  • Natural ventilation shaft
  • Powered extraction shaft

A full design report including all calculations shall be provided for submission to Building Control prior to installation.

The design, manufacture, installation, wiring and commissioning of the complete system, including associated ductwork, shall be carried out by one specialist company and their approved sub-contractors. The specialist company shall be responsible for demonstrating and gaining Building Control approval for the pressurisation system. The specialist company shall also provide the accommodation air release system.

The specialist company shall be a BSI registered firm for the design, manufacture, installation and commissioning of smoke control systems in accordance with ISO 9000. Proof of certification shall be provided with tender submission.

The system will require annual maintenance and testing. The supplier shall include in the tender for a service visit and system test to be carried out one year after system hand over.

Air Release Natural Shaft

Accommodation air release for the pressurisation system shall be provided by means of a natural ventilation shaft.

The shaft shall be of fire resistant construction and shall be substantially straight and vertical, terminating in a Colt Seefire ventilator, type LS/.. to provide weatherproof closure when the system is not in use.

The shaft shall have a minimum cross sectional area sized to handle the design flow rate from the pressurisation system onto the fire floor under open door conditions at a maximum velocity of 2m/s.

At each storey of the accommodation an automatically controlled fire rated smoke damper / fire door with a cross sectional area at least equal to that of the shaft shall be connected to the shaft, providing an air flow path from the accommodation to the shaft. A low resistance decorative grille or louvre shall be provided in front of each damper. / The fire doors and any guarding necessary to avoid risk of falls through them will be provided by others. Operation of the doors shall be by the Colt Doorman actuator system.

Power to the system shall be provided from a maintained supply and all cables shall be fire resistant. The maintained supply (by others) shall terminate at a changeover panel close to the accommodation air release control panel location. All wiring from this point shall be the responsibility of the system supplier. / The system shall operate at 24 / 12 Volts and shall incorporate a battery back up system. Mains power (by others) shall be provided close to the accommodation air release control panel location. All wiring from this point shall be the responsibility of the system supplier.

In automatic mode, the system shall be activated by the building fire detection system / a dedicated fire detection system incorporating smoke detectors in the accommodation adjacent to each door into the stairwell protected shaft and supplied as part of the accommodation air release system. The detection system shall have the capability of distinguishing on which storey the fire occurs and providing a dedicated output for each storey.

Under fire conditions the Seefire ventilator and the damper / door on the fire floor shall open. The dampers / doors on all other storeys shall remain closed. The Colt OPV addressable control system shall be used to provide this facility.

The control panel or a mimic panel for fire service use shall be mounted in a position accessible to and agreed with the fire service and shall incorporate status indication and manual override for fire service use. The control panel or mimic panel shall be either combined with the panel for the pressurisation system or shall be mounted adjacent to it.

Indication shall be provided for:

  • Power supply available - green
  • Termination open - green
  • Damper /Door open - green (one per storey)
  • Fire condition - red

Fire override control shall be provided for:

  • Damper
  • Door close
  • Auto
  • Open (one per storey)

The design, manufacture, installation,wiring and commissioning of the complete system shall be carried out by one specialist company and their approved sub-contractors. The specialist company shall also provide the pressurisation system and shall be responsible for gaining Building Control approval for the complete pressurisation and accommodation air release system.

Air Release Powered Shaft

Accommodation air release for the pressurisation system shall be provided by means of powered extract, drawing air and smoke from the fire floor via a shaft.

The system shall incorporate duty and standby fans with automatic change over, mounted on the roof / in a separate plant room / in a general plant room / at ground level. The fans shall comply with BS EN 12101-3 / 7346 part 2 and shall be rated to operate at -oC for .. minutes. The fans shall be rated to provide an extract rate from the fire floor at least equal to the design air flow rate from the pressurisation system onto the fire floor in the open door condition.

The shaft and any associated ductwork shall be of fire resistant construction and shall terminate in a Colt Seefire ventilator, type LS/.. to provide weatherproof closure when the system is not in use.

At each storey of the accommodation an automatically controlled fire rated smoke damper / fire door shall be connected to the shaft, providing an air flow path from the accommodation to the shaft. A decorative grille or louvre shall be provided in front of each damper. / The fire doors and any guarding necessary to avoid risk of falls through them will be provided by others. Operation of the doors shall be by the Colt Doorman actuator system.

Power to the system shall be provided from a maintained supply and all cables shall be fire resistant. The maintained supply (by others) shall terminate at a changeover panel close to the accommodation air release control panel location. All wiring from this point shall be the responsibility of the system supplier.

In automatic mode, the system shall be activated by the building fire detection system / a dedicated fire detection system incorporating smoke detectors in the accommodation adjacent to each door into the stairwell protected shaft and supplied as part of the accommodation air release system. The detection system shall have the capability of distinguishing on which storey the fire occurs and providing a dedicated output for each storey.

Under fire conditions the Seefire ventilator and the damper / door on the fire floor shall open and the duty fan shall run. The dampers / doors on all other storeys shall remain closed. Upon failure of the duty fan it shall be automatically disconnected and the standby fan shall automatically run. The Colt OPV addressable control system shall be used to provide this facility.

The control panel or a mimic panel for fire service use shall be mounted in a position accessible to and agreed with the fire service and shall incorporate status indication and manual override for fire service use. The control panel or mimic panel shall be either combined with the panel for the pressurisation system or shall be mounted adjacent to it.

Indication shall be provided for:

  • Power supply available - green
  • Fan 1 run / flow proven - green
  • Fan 2 run / flow proven - green
  • Fan 1 fault - amber
  • Fan 2 fault - amber
  • Termination open - green
  • Damper /Door open green (one per storey)
  • Fire condition - red

Fire override control shall be provided for:

  • Fan 1 - off / auto / run
  • Fan 2 - off / auto / run
  • Damper / Door close / auto / open (one per storey)

The design, manufacture, installation, wiring and commissioning of the complete system shall be carried out by one specialist company and their approved sub-contractors. The specialist company shall also provide the pressurisation system and shall be responsible for demonstrating and gaining Building Control approval for the complete pressurisation and accommodation air release system.

Air Release Ventilators

Accommodation air release for the pressurisation system shall be provided by means of automatically opening ventilators to each storey of the accommodation.

The ventilators shall be Colt Kameleon / Coltlite type / other , mounted vertically and spread over at least two opposing facades to the accommodation.

The ventilators shall comply with the requirements of EN 12101-2.

The ventilators on each storey shall have a minimum open area sized to handle the design flow rate from the pressurisation system under open door conditions at a maximum velocity of 2.5m/s with the ventilators on the façade with the largest ventilation area discounted to allow for adverse wind effects.

Power to the system shall be provided from a maintained supply and all cables shall be fire resistant. The maintained supply (by others) shall terminate at a changeover panel close to the accommodation air release control panel location. All wiring from this point shall be the responsibility of the system supplier. / The system shall operate at 24 / 12 Volts and shall incorporate a battery back up system. Mains power (by others) shall be provided close to the accommodation air release control panel location. All wiring from this point shall be the responsibility of the system supplier.

In automatic mode, the system shall be activated by the building fire detection system / a dedicated fire detection system incorporating smoke detectors in the accommodation adjacent to each door into the stairwell shaft and supplied as part of the accommodation air release system. The detection system shall have the capability of distinguishing on which storey the fire occurs and providing a dedicated output for each storey.

Under fire conditions the ventilators on the fire floor shall open. The ventilators on all other storeys shall remain closed. The Colt OPV addressable control system shall be used to provide this facility.

The control panel or a mimic panel for fire service use shall be mounted in a position accessible to and agreed with the fire service and shall incorporate status indication and manual override for fire service use. The control panel or mimic panel shall be either combined with the panel for the pressurisation system or shall be mounted adjacent to it.

Indication shall be provided for:

  • Power supply available - green
  • Ventilators open - green (one per storey)
  • Fire condition - red

Fire override control shall be provided for:

  • Ventilators close / auto / open (one per storey)

The design, manufacture, installation, wiring and commissioning of the complete system shall be carried out by one specialist company and their approved sub-contractors. The specialist company shall also provide the pressurisation system and shall be responsible for gaining Building Control approval for the complete pressurisation and accommodation air release system.

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