5.1

5.1 Spaces to Be Pressurised

5.1.1 Stair 1 (Above Ground Floor) + Fire lobbyStair 1 is constructed from Ground floor to roof level. It is connected through fire lobbies to accommodation areas. There is a single leaf door (1mx2.1m (H)) for staircase and there are two double leaf doors (1.4mx2.1m (H)) separating the lobbies and accommodation areas. The staircase and the fire lobby will be pressurised independently. There is a fire lift within each fire lobbies. The fire lift shaft will be pressurised bythe supply air from the lobbies through leakage path of lift landing doors.

Design Pressurization Level in Stair = 50Pa.Design Pressurization Level in Fire Lobby = 45Pa.

5.1.2 Stair 2 (Above Ground Floor) + Fire lobbyStair 2 is constructed from Ground floor to roof level. It is connected through fire lobbies to accommodation areas. There is a single leaf door (1mx2.1m (H)) for staircase and there are two double leaf doors (1.4mx2.1m (H)) separating the lobbies and accommodation areas. The staircase and the fire lobby will bepressurised independently. There is a fire lift within each fire lobbies. The fire lift shaft will be pressurised bythe supply air from the lobbies through leakage path of lift landing doors.

Design Pressurization Level in Stair = 50Pa.Design Pressurization Level in Fire Lobby = 45Pa.

5.1.3 Stair 1 (Below Ground Floor) + Fire lobbyStair 1 is constructed from B2 up to Ground Floor. It is connected through fire lobbies to accommodation areas. There is a single leaf door (1mx2.1m (H)) for staircase and there are two double leaf doors (1.4mx2.1m (H)) separating the lobbies and accommodation areas. The staircase and the fire lobby will be pressurised independently. There is a fire lift within each fire lobbies. The fire lift shaft will be pressurised bythe supply air from the lobbies through leakage path of lift landing doors.

Design Pressurization Level in Stair = 50Pa.Design Pressurization Level in Fire Lobby = 45Pa.

5.1.4 Stair 2 (Below Ground Floor) + Fire lobbyStair 2 is constructed from B2 up to Ground Floor. It is connected through fire lobbies to accommodation areas. There is a single leaf door (1mx2.1m (H)) for staircase and there are two double leaf doors (1.4mx2.1m (H)) separating the lobbies and accommodation areas. The staircase and the fire lobby will be pressurised independently. There is a fire lift within each fire lobbies. The fire lift shaft will be pressurised bythe supply air from the lobbies through leakage path of lift landing doors.

Design Pressurization Level in Stair = 50Pa.Design Pressurization Level in Fire Lobby = 45Pa.

5.1.5 Stair 3Stair 3 is constructed from Ground Floor to fifth floor. There is a single leaf door (1mx2.1m (H)) separating the staircase and accommodation areas.

5.2 Code of Design

5.2.1 BS EN 12101-6:2005.5.2.2 Uniform Building By Law

5.3 Calculation of Supply Air Requirement

5.3.1 Staircase 1 & Lift Lobby Pressurization System

5.3.1.1 Based on Class-B Pressure Differential System

5.2

Design condition: In the event of fire, all the following doors open between ~Stair/lobby on the fire affected floor;~Stair/lobby on the floor below fire affected floor;~Lobby/accomodation area on the fire affected floor (minimum air velocity=2m/s);~Final exit door.

5.3.1.1.1 Staircase 1 - Leakage Through Closed DoorsThere are 34 nos. of 1mx2.1m(H) doors opening into the pressurised staircase and 1 no. of 1mx2.1m(H) door opening outward from pressurised staircase at ground floor.

a) Leakage area for 0.8mx2m(H) single leaf door opening =into pressuried space

Leakage area for 0.8mx2m(H) single leaf door opening =opening outwards from pressuried spaceCrack length for 0.8mx2m(H) door = (0.8+2)2

= 5.6m

b) Crack length for 1mx2.1m(H) single leaf door = (1+2.1)2= 6.2m

Leakage area for 1mx2.1m(H) single leaf door opening = (6.2/5.6)0.01

into pressuried space =Leakage area for 1mx2.1m(H) single leaf door opening = (6.2/5.6)0.02

outwards from pressuried space =

c) Airflow required in staircase 1 at =

closed door condition = 1.110(Add 50% safety factor for unidentified leakage paths)

5.3.1.1.2 Lift Lobby - Leakage Through Closed DoorsOn every floor level, there are 2 nos. of 1.4mx2.1m(H) doors and 1 no. of lift landing door opening into pressurised lobby. But at ground floor, the 2 nos. of 1.4mx2.1m(H) doors are opening outward from its pressurised lobby.

a) Leakage area for 1.6mx2m(H) double leaf door =Crack length for 1.6mx2m(H) double leaf door = (1.6+2)2+2

= 9.2mCrack length for 1.4mx2.1m(H) double leaf door = (1.4+2.1)2+2.1

= 9.1mLeakage area for 1.4mx2.1m double leaf door is to be same as leakage area for 1.6mx2m double leaf door.

Leakage through 1.4mx2.1m(H) double leaf door =

= 0.167

b) Leakage area for each lift landing door =Leakage through all lift landing doors =

= 0.556

c) Airflow required in lift lobby at = [(0.556/41)+(2x0.167)]x1.5closed door condition = 0.521(Add 50% safety factor for unidentified leakage paths)

5.3.1.1.3 Staircase 1 & Lift Lobby at Opened Doors Condition

a) Airflow past through door of = 1.110x(1x2.1)/[(1x2.1)+(1x2.1)+(2x0.03)+0.06]staircase 1/lobby = 1.11x0.486

= 0.540

b) Airflow past through door of lobby/accomodation = 0.540+0.521

0.01 m2

0.02 m2

0.0111 m2

0.022 m2

0.83x[34x(6.2/5.6)0.01x5(1/2)+1x(6.2/5.6)0.02x5(1/2)]x1.5

m3/s

0.03 m2

0.83x0.03x45(1/2)

m3/s

0.06 m2

0.83x((0.06x41)-2+0.1-2)-1/2x45(1/2)

m3/s

m3/s per floor

m3/s

5.3

= 1.061 m3/s

5.4

c) Velocity through door of lobby/accomodation = 1.061/(0.7x2.1)(assume one leaf of Double leaf door is in = 0.722opened position during firefighting) (but < 2m/s as recommended)

d) Airflow needs to be added to the lift lobby = (2-0.722)x(0.7x2.1)

= 1.879

e) Airflow needs to be added to the staircase 1 = 1.879x(1/0.486)

= 3.866

f) The minimum airflow required for staircase 1 pressurization Fan = 3.866+1.11

(excluding duct leakage) = 4.976(10544 cfm)

5.3.1.2 Based on Class-E Pressure Differential System Design condition: In event of fire, all the following doors open between ~Stair/lobby on the fire affected floor;~Stair/lobby on the floor above fire affected floor;~Lobby/accomodation area on the floor above fire affected floor;~Lobby/accomodation area on the fire affected floor (minimum air velocity=0.75m/s);~Final exit door.

5.3.1.2.1 Staircase 1 & Lift Lobby at Opened Doors Condition (considering initial stage of fire before firefighting)

a) Airflow past through door of staircase 1/lobby = 4.976/3

= 1.659

b) Airflow past through door of lobby/accomodation = 1.659+0.521

= 2.180

c) Velocity through door = 2.180/(1.4x2.1x2) (assume 2 nos. of 1.4mx2.1m double leafof lobby/accomodation door open simultaneously)

= 0.371 (but < 0.75m/s as recommended)

d) Airflow needed to be increased for lift lobby = (0.75-0.371)x(1.4x2.1x2)

= 2.229

e) The minimum airflow required for lift lobby = 2.229+0.521

(excluding duct leakage) = 2.750 (5827 cfm)

5.3.1.3 Based on Combination of Class-B and Clase-E Pressure Differential System This design condition is the worst scenario among Class-B and Class-E. It is based on the assumption that the fire is no longer at early stage, occupants from other two floors (which are non-fire-affected floors) are being evacuated out of the building when firefighting is still in progressing.

5.3.1.3.1 Staircase 1 & Lift Lobby at Opened Doors Condition

a) Air flow past open door of staircase 1/lobby on fire affected floor= 4.976x(1x2.1)/[(1x2.1)(4)+(2x0.03)+0.06]

= 1.226

b) Velocity thru door of the lobby/accomodation on fire affected floor (assume one leaf of double leaf

= (1.226+2.750)/(0.7x2.1) door is in opened position during

= 2.705 (> 2m/s as recommended) firefighting)

5.3.1.4 Capacity of Staircase 1 Pressurization Fan= 4.976x1.15

= 5.722 (12124 cfm)

m/s

m3/s

m3/s

m3/s

m3/s

m3/s

m/s

m3/s

m3/s

m3/s

m/s

m3/s

5.5

5.3.1.5 Capacity of Lift Lobby Pressurization Fan= [(3x2.750)+(38x0.521)]x1.15

= 32.255 (68345 cfm)

5.3.2 Staircase 3 Pressurization System

5.3.2.1 Based on By-Law: Pressurised System for Staircase Design condition: 10% of door open with minimum 2 doors (Velocity=1m/s)

5.3.2.1.1 Staircase 3 at Opened Doors Condition

a) Staircase 3 airflow required at opened door condition =

= 6.33

b) Capacity of staircase 3 Pressurization fan = 6.33 x1.15

= 7.283 (15432 cfm)(Add 15% safety factor for duct leakage)

5.4 Quantity of Air Relief To ensure proper working of pressurization system as planned, means of air relief has to be incorporated into the system to give sufficient leakage of pressurised air from accomodation area to exterior of the building. Based on Class-E scenario, whereby two nos. of 1.4mx21.m double leaf doors open into accomodation area, the quantity of air relief required isestimated as follows,

Air relief quantity = 2x2.1x1.4x0.75

= 4.410 (9344 cfm)

m3/s

(0.011m2x3)+3(1mx2.1m)

m3/s

m3/s

m3/s

5.6

5.5 Airflow Criterion for Respective Classes

Figure 5.1: Design Conditions for Class-B System Figure 5.2: Design Conditions for Class-E System

Figure 5.3: Design Conditions for Combination of Class-B and Class-E System