I would like to design stair pressurisation & lobby pressurisation fans for a 24 storey residential building.I would like to get the help of some body to make design calculation for the capacity of fans asper NFPA standards.

He Gopikn



a- For High Storey Building: Assuming 2 door opening.

Area of open door ( A ) = 2 x 0.9 = 1.8 m2

Egrees velocity ( Ve ) = 0.75 m/s ( across open door )
Total Air Flow (Qs ) = Ve x n x A / 0.6 = 4.5 m3/s = 9,534 cfm
( Through open door )

b- Leakage Through Closed Doors

Leakage area of double leaf door ( Al ) = 0.02 m2
Total number of closed doors (nl ) = 26 Nos.
( K ) = 0.829
( p ) = 50
Total Air leakage (Ql) = K x nl x Al x p0.5 = 3.048195912 m3/s = 6,458 cfm
Add 25%, So Ql = 8072.552734 CFM

Select the higher of the two --- Q = 9534 CFM

You can check application ASHRAE standard chapter A52 of 2007 it include on a clear description on how to size preesurzation system and a very valuable data in this regard. ASHRAE data comply with NFPA recommendations.