Stair 1 (Above Ground Floor) + Fire lobby Stair 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 by the 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 lobby Stair 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 be pressurised independently. There is a fire lift within each fire lobbies. The fire lift shaft will be pressurised by the 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 lobby Stair 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 by the 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 lobby Stair 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 by the 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 3 Stair 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 5.2.2
BS EN 12101-6:2005. 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 5.1
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 Doors There 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 space Crack length for 0.8mx2m(H) door = =
=
0.01 m2
=
0.02 m2
b) Crack length for 1mx2.1m(H) single leaf door
= = = = = =
Leakage area for 1mx2.1m(H) single leaf door opening into pressuried space Leakage area for 1mx2.1m(H) single leaf door opening outwards from pressuried space
c) Airflow required in staircase 1 at = 0.83x[34x(6.2/5.6)0.01x5(1/2)+1x(6.2/5.6)0.02x5(1/2)]x1.5 m3/s closed door condition = 1.110 (Add 50% safety factor for unidentified leakage paths) 5.3.1.1.2 Lift Lobby - Leakage Through Closed Doors On 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. 0.03 m2 = = (1.6+2)2+2 = 9.2m Crack length for 1.4mx2.1m(H) double leaf door = (1.4+2.1)2+2.1 = 9.1m Leakage 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 = 0.83x0.03x45(1/2) = 0.167 m3/s
a) Leakage area for 1.6mx2m(H) double leaf door Crack length for 1.6mx2m(H) double leaf door
b) Leakage area for each lift landing door Leakage through all lift landing doors
c) Airflow required in lift lobby at = [(0.556/41)+(2x0.167)]x1.5 closed door condition = 0.521 m3/s per floor (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 staircase 1/lobby
b) Airflow past through door of lobby/accomodation 5.2
=
0.540+0.521
=
5.3
1.061 m3/s
c) Velocity through door of lobby/accomodation (assume one leaf of Double leaf door is in opened position during firefighting)
= =
1.061/(0.7x2.1) 0.722 m/s (but < 2m/s as recommended)
d) Airflow needs to be added to the lift lobby
= =
(2-0.722)x(0.7x2.1) 1.879 m3/s
e) Airflow needs to be added to the staircase 1
= =
1.879x(1/0.486) 3.866 m3/s
f) The minimum airflow required for staircase 1 pressurization Fan (excluding duct leakage)
= 3.866+1.11 m3/s = 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 m3/s
b) Airflow past through door of lobby/accomodation
= =
1.659+0.521 2.180 m3/s
c) Velocity through door = of lobby/accomodation =
(assume 2 nos. of 1.4mx2.1m double leaf door open simultaneously) (but < 0.75m/s as recommended)
2.180/(1.4x2.1x2) 0.371 m/s
d) Airflow needed to be increased for lift lobby
e) The minimum airflow required for lift lobby (excluding duct leakage)
= = = =
(0.75-0.371)x(1.4x2.1x2) 2.229 m3/s
2.229+0.521 2.750 m3/s
(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 m3/s b) Velocity thru door of the lobby/accomodation on fire affected floor = (1.226+2.750)/(0.7x2.1) = 2.705 m/s (> 2m/s as recommended) 5.3.1.4 Capacity of Staircase 1 Pressurization Fan = 4.976x1.15 = 5.722 m3/s (12124 cfm) 5.4
(assume one leaf of double leaf door is in opened position during firefighting)
5.5
5.3.1.5 Capacity of Lift Lobby Pressurization Fan = [(3x2.750)+(38x0.521)]x1.15 = 32.255 m3/s (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
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 m3/s
(9344 cfm)
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 5.7
