Colt Mechanical Shaft: protecting means-of-escape stairs in residential and fire-fighting stairs

Colt Mechanical Shaft is a mechanical fire fighting shaft system which provides equivalent performance to a BRE shaft for the ventilation of common corridors and fire fighting lobbies. It can therefore be considered to meet the recommendations of Approved Document B, BS9991 and BS 9999 for ventilation of stair cores. 

Under design conditions with the lobby doors open, ColtShaft provides a ventilation rate similar to the BRE shaft. 

Product information

Space saving

Colt Mechanical Shaft requires a shaft with a cross sectional area which can be as small as only 0.6m² compared with 3m² for the BRE shaft or 1.5m² for a natural residential (ADB) shaft.

This represents up to 80% reduction in the floor space required. It opens up the space on each floor, which allows architects to be more creative in their design, and improves the saleable or lettable space for the client. This in turn increases the profits for developers and the income for landlords, and permits more usable space.

Enhanced performance

Colt Mechanical Shaft can perform better than a BRE Shaft since it extracts at a defined rate - this means that it is unaffected by external wind pressures. It is also less susceptible to obstructions to the airflow within the duct.

View our ColtShaft system under test for more information.

The Colt Mechanical Shaft design has been proven by extensive CFD analysis and by empirical tests.

There are two types of Colt Mechanical Shaft, the ColtShaft (Variable) and the ColtShaft (Constant).

ColtShaft (Variable) system

The ColtShaft (Variable) incorporates duty and standby variable speed extract fans with inverter drive, linked to pressure sensors within the lobby and corridor at each level via the control panel. A motorised damper or flap is provided between the shaft and the lobby/corridor at each level. A 1 mventilator is needed in the stairwell for air inlet.

The pressure sensors maintain acceptable pressure difference between the lobby and stairs, typically at 25Pa.  This ensures that excess pressures do not draw extra smoke past door seals or cause excessive door opening forces.

ColtShaft (Constant) system

The preferred design of mechanical shaft for apartment buildings is the ColtShaft (Variable).  However, not all clients are prepared to make the investment needed for this system. The ColtShaft (Constant) provides equal or better ventilation, but at the expense of potentially compromising compartmentation and of reverse hanging escape doors to open against the direction of escape. It has a lower initial cost.

The ColtShaft (Constant) uses a fixed speed fan, sized to provide the full ventilation rate when the stair door is open. To avoid over depressurisation of the lobby or corridor when the doors are closed, an adjustable door closer is provided to the stair door which can be set to allow the door to be pulled open sufficiently to maintain a set pressure difference, normally around 25Pa. To allow this, the doors opening onto the lobby or corridor should be reverse hung to be pulled open by escaping occupants rather than opening in the direction of escape as is the conventional practice.

Product video

Compliant AOV solution

Colt Extended Corridor solution

This clip shows a CFD model of a Building Regulations compliant dead-end corridor fitted with a conventional AOV. Smoke is shown blue and clear air is shown red. At the start of the video the door opens to allow people to escape and smoke pours out of the apartment and hangs around in the corridor. The video then jumps forward to when the fire brigade arrive to open the door again to fight the fire. The corridor fills with smoke. The corridor remains smoke logged for a long time after the door is re-closed.

This clip shows a CFD model of a non-compliant dead-end corridor provided with an Extended Corridor "Pull" system to compensate for extended travel distances. Smoke is shown blue and clear air is shown red. At the start of the video the door opens to allow people to escape and smoke pours out of the apartment but is quickly cleared. The video then jumps forward to when the fire brigade arrive to open the door again to fight the fire. The corridor fills with smoke but it then clears quickly when the door is re-closed. By comparison with the situation with a conventional AOV, the Colt Extended Corridor "Pull" system provides better conditions for escape and fire-fighting.

ColtShaft Variable options

Description

The ColtShaft (Variable) system comprises:

  • Duty and standby extract fans rated at 300°C for 1 hour
  • Colt Seefire duct termination
  • Colt Seefire stairwell ventilator
  • Ducting to link builders work shaft (by others) to fans and duct termination
  • Either a motorised smoke damper and grille or Defender F flap ventilator to each lobby (minimum E30S rated)
  • MCC/Fan starter panel linked to main control panel
  • Pressure sensor to each lobby
  • Smoke detector to each lobby.

Builders work requirements

The builders work shaft is to be substantially straight, vertical and directly adjacent to the lobbies. The construction is to have a smooth internal face and minimum air leakage. The internal cross section is to be no less than 0.6m2 and the aspect ratio no greater than 2:1.

Please note that it is possible that the ducting is in a location that requires fire rated ducting.

A full generic design report 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 ventilation 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 the system hand over.

ColtShaft Constant options

Description

The ColtShaft (Constant) system comprises:

  • Duty and standby extract rated at 300ºC for 1 hour
  • Colt Seefire duct termination
  • Colt Seefire stairwell ventilator
  • Ducting to link builders work shaft to fans and duct termination
  • Motorised [smoke damper and grille/flap/fire door] to each lobby
  • Main control panel plus fire fighter’s panel for fire service use
  • Adjustable door closer for each door between stair and lobbies
  • Smoke detector to each lobby

Builders work requirements 

The builders work shaft is to be substantially straight & vertical and will connect to the lobbies at each level via a 1 hour fire rated damper and grille, connected if necessary by a short 1 hour fire rated horizontal duct. The construction of the builders work shaft is to have a smooth internal face and minimum air leakage. The internal cross section of the shaft and duct is to be no less than 0.6m2 and the aspect ratio no more than 2:1.

The fire door between the stair and the lobby is to be hung to open into the lobby. No door closer should be fitted as an adjustable door closer will be fitted by Colt.

The fire door between the lobby and the accommodation is to be fitted with smoke seals (FD30S rating) and hung to open away from the lobby.

A full generic design report 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 ventilation 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 the system hand over.

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