The Application of Stair Pressurisation to Crossrail Stations, Shafts and Portals

Summary

This paper reviews the design of the stair pressurisation and air release system used in the pressure differential system for protected areas designated for firefighting. They are referred to as firefighting shafts as defined in BS9999. Potential deviations from BS EN 12101 Part 6 are also discussed in this paper.

Fire Stair Cores are provided at stations, shafts and portals. Depending on building configuration, the Fire Fighting Core consists of a stair case, lift shaft and firefighting lobbies. The fire stair core is intended to provide a protected access route in the building for fire brigade in the event of a fire alarm. It may also provide an escape route during the first instance of fire detection to evacuate the building.

BS9999 states that a firefighting shaft must be designed to meet the requirements of Class B as set out in BS EN 12101-6: 2005 where it has to be pressurised. However, strict compliance with this is not necessarily required.

The purpose of the stair pressurisation systems is to maintain tenable conditions to the firefighting shaft by preventing smoke propagation from the accommodation areas into the shaft. The intent being to keep these protected areas clear of smoke. This is achieved by the use of pressure differential systems pressurising the protected space with air drawn from outside and a release path for air escaping from the protected space to the fire affected area.