Mechanical ventilation system for car parks in fire conditions

a system of mechanical ventilation where – (i) the system is independent of any other ventilation system and designed to operate at 6 air changes per hour for normal extraction and at 10 air changes per hour in a fire condition; (ii) the system is designed to operate in two parts, each capable of extracting 50% of the rates set out in (i) above and designed so that each part may operate singly or simultaneously; each part of the system should have an independent power supply which will operate in the event of failure of the main supply; (iii) extract points are arranged so that 50% are at high level and 50% at low level; and (iv) the fans are rated to run at 300ºC for not less than 60 minutes, and the ductwork and fixings are constructed of materials having a melting point of not less than 800ºC.