Attachment 2 - Method Statement.docx

Pressurisation according to BS EN 12101-6: 2005 The purpose of a pressurisation system is to protect the pressurised areas from smoke ingress in case of fire by keeping the pressure higher than in the room where the fire occurs and by ensuring a positive air flow into the fire room if the connecting door is opened.

BS EN 12101-6:2005 sets the requirements for pressurisation of stair cores within the United Kingdom. 5 classes of system are detailed within the standard:

- Class A Buildings with a ‘defend in place’ strategy (typically residential).

- Class B Protection of fire fighting shafts.

- Class C Means of escape through simultaneous evacuation.

- Class D Buildings where occupants may be sleeping, e.g. hotels and hostels.

- Class E Means of escape through phased evacuation.

The three systems that are provided for this building are a combination of Class B & Class C. The spaces to be pressurised as part of the Class B system are Stair 3, the Fire Fighting Lift Lobby & the Fire Fighting Lift. The spaces to be pressurised as part of the Class C systems are Stair 1 and Stair 2.

With all doors closed the system is intended to provide a pressure differential relative to the main corridor of 50Pa in the stairs, 50Pa in the fire fighting lift and 45Pa in the fire fighting lobby. A tolerance of ± 5Pa is normally permitted.

With selected doors open, the system is intended to maintain an air velocity through the door between the stairs and main corridor of at least 0.75m/s (2.0m/s for Class B).

With selected doors open the Class C systems are also intended to provide a pressure differential of 10Pa in the stairs.

There are some areas within the building where accommodation air release cannot be achieved due to the layout of the building. A means of air release from the main corridor is required. This is to maintain the open door conditions to ensure that the main corridor does not become pressurised if the door is held open for any length of time. This is achieved by means of a mechanical extract shaft, serving each floor adjacent to Lift 4.

However, the effect of this is minimal as there are 3 protected stairs within the building, all of which can be accessed from every floor.

In the unlikely event that one stair to fail due to the lack of accommodation air release, alternative escape routes will be available via the two remaining stairs. Although this is a deviation from the guidance given in BS EN 12101-6: 2005, it does not pose a significant risk to the safety of the building and its occupants.

PROCEDURE FOR TESTING OF STAIR PRESSURISATION SYSTEMS

1. Introduction This procedure covers functional testing of a pressurisation system. It does not cover the normal mechanical and electrical testing of the pressurisation equipment.

The testing procedure conforms to the requirements of BS 5588-4:1998 and BS EN 12101-6:2005.

Functional testing should not be carried out on days with high winds or blustery conditions as these may affect the accuracy of the results.

2. Equipment required Micromanometer and flexible tube. Minimum range -100Pa to +100Pa.

Rotating vane anemometer. 100mm diameter recommended. Minimum range 0 to 10m/s.

Spring balance. Minimum range 0 to 15kgf (0 to 150N).

Door wedges (optional).

Warning notices for doors: “Stair pressurisation under test. Please do not enter” (optional).

Pitot tube (to check fan air flow rate if believed deficient optional).

Equipment should have a current calibration certificate (if applicable).

Spare batteries are recommended.

3. Pre-test inspection By inspection of documentation, drawings or the physical installation establish as far as possible:

- Age of system (and hence which standard applies)

- Which class of system is installed (post 1998 only)

- Which areas are pressurised (stair only, stair + lobbies, Stair + lifts, stair + lobbies + lifts)

- Method of stair pressure control (pressure relief damper or pressure sensor and inverter)

- Method of accommodation air release (general building leakage, façade ventilators, natural shaft or mechanical shaft).

- Design air flow rate.

Walk through the pressurised areas and note any obvious faults or problems (damaged or blocked pressurisation air supply grilles, doors wedged open, doors not closing properly, unsealed openings around cables, pipes or ducts, etc). Leave all doors closed.

If using warning notices for doors, Blu-tack them in place during this walk round.

Inspect the pressurisation plant and note any obvious faults or problems.

Note: If any major problems are found during this pre-test inspection it may be necessary to delay testing until the problems are rectified.

Decide which floors to carry out testing on. For small buildings (<6 storeys pressurised) test every floor. For taller buildings test a representative sample of floors, but at least 6. If any problems are identified during testing the representative sample, it may be necessary to carry out full or partial testing of further floors to identify the extent of the problem.

4. Conditioning Operate the pressurisation system. Allow the system to run for at least 10 minutes to establish steady air temperatures.

Switch off any ventilation or air conditioning systems which are interlocked to off by the fire detection system.

During this period inspect the pressurisation plant to ensure that the fan is operating correctly and that necessary ventilators and/or dampers have opened correctly.

Switch off the pressurisation fan.

5. Pressure test with system off On each floor to be tested, open and re-close each door to the pressurised area and then measure the pressure differential across each door separating pressurised and unpressurised areas using the micromanometer and tubes. The ends of the tubes should either be raised at least 50mm above floor level or should be located so that they are not affected by any draughts passing under the doors.

The pressure differentials measured should be close to zero. The reasons for any unusually high readings should be investigated and rectified as necessary.

6. Pressure test with system operating Switch the pressurisation system fully on, with the accommodation air release open on the floor to be tested. This will require resetting for each floor tested.

With all doors closed, measure the pressure differential between each pressurised area and each unpressurised area with a door to a pressurised area.

Note: If the measurement tubes are too short for this it is permissible to measure the pressure differential in sections and sum them, for example by measuring between the stair and the lobby and then between the lobby and the unpressurised area.

The results of the testing will be recorded on MS Excel document 240101 MASTER TEMPLATE FOR STAIR 3 PRESSURISATION RECORDS that is stored in Colt file SC1/4522. This sheet will be issued with the certificate following the annual PPM visit.