BS 9999 | Ch. 15 | Fig. 6c

Merging flow from stairs from above and below, combined with storey exit

Calcualtes the merging flow from stairs above and below the final exit level, combined with with storey exit

Reference

British Standards Institution, 2017. BS 9999: Fire safety in the design, management and use of buildings - Code of practice. BSI.

Equations

W_{FE} = S_{up} + S_{dn} + W_{SE} or W_{FE} = B \cdot X + N \cdot X + 0.75 \cdot S_{up}

Number of people served by the stair from below the final exit level ( B )

Number of people served by the final exit level storey exit ( N )

Lesser distance from the final exit level storey exit or the lowest riser from the upward portion of the stairs ( D ) — m

Stair width for upward portion of the stair ( S_{up} ) — mm

Stair width for downward portion of the stair ( S_{dn} ) — mm

Width of the final exit level storey exit ( W_{SE} ) — mm

Minimum door width per person ( X ) — mm/person