$($b$)$ A staircase pressurization system is adopted in a commercial building with designated floors $($G$/$F$,1/$F to $29/$F & R$/$F$)$ at Wan Chai. The design pressure with all doors closed and all over pressure relief systems in operation shall be $50$ Pa minimum in accordance with BS$5588$ Part $4.$ The typical floor plan of escape doors and details of the doors are shown in Figure Q$5\mathrm{.}3,$ Table Q$5\mathrm{.}1$ and Table Q$5\mathrm{.}2$ respectively. It is assumed that there is no natural ventilation at staircase and the headroom of each floor is at the height $3\mathrm{.}2$ m $.$

$($i$)$ Determine the total air leakage across remaining doors.

$(4$ marks$)$

$($ii$)$ Determine the design air supply flow rate for the pressurization system.

$(5$ marks$)$

$($iii$)$ State the multiple injection requirements with air supply and estimate the minimum number of injection points.

$(3$ marks$)$

$\backslash$table$[[$Type of building:,Commercial building$],[$Floor:$,$G$/$F$,1/$F to $29/$F & R$/$F$],[$Staircases:$,$No natural ventilation$]]$

Table Q$5\mathrm{.}1$

$\backslash$table$[[$Floor$,$Door type,$\backslash$table$[[$Door$],[$Dimension $($m$)]],\backslash$table$[[$Effective Leakage$],[$Area$]]],[$G$/$F Exit Door,$\backslash$table$[[$Double leaf door with or without center$],[$rebated frame$]],2\mathrm{.}21\mathrm{.}8,\backslash$table$[[0\mathrm{.}03m^2$