Ventilation for non-open-sided car parks

Where a car park does not comply with the provisions of paragraph 4.50 it should not be regarded as open-sided for the purposes of Table 4.2 [i.e. it falls in Purpose Group 7(b)(ii)]. However, there is a need for ventilation in such a car park, therefore in addition to the provisions of paragraph 4.49 it should have either – (a) natural ventilation at each storey – (i) by permanent openings at each car parking level, having an aggregate ventilation area of not less than 2.5% of the floor area at that level, with not less than half that ventilation area equally divided in two opposing walls and distributed to provide effective cross-ventilation; or (ii) by suitable vents at ceiling level on each car parking level having an aggregate area of permanent opening not less than 2.5% of the floor area and so arranged as to have a through flow of air; or