(a) Each room in which a dry cleaning machine is installed shall have normal mechanical ventilation by means of an exhaust system having its intake opening substantially at floor level and capable of providing ventilation rates as follows:

(b) In addition to the normal mechanical ventilation above required, there shall be installed in each service area a fan or other exhaust system reserved for and capable of being operated in an emergency and affording a ventilation rate per machine of 500 cfm in combination with the maximum rate of the normal system.

(c) At all times when a dry cleaning machine is available for normal operation, mechanical ventilation shall be maintained sufficient to prevent formation of dangerous air contaminants in any room or area in which the machine is wholly located or partly located.

(d) The flow of ventilation shall be from the normal outdoor atmosphere to the customer area and thence through the service area to outdoors, discharging in such place and manner as to prevent recirculation into the customer area.

(e) Ventilation fans shall be operable regardless of operation of machines.

(f) A minimum inward velocity of 100 lfm shall be maintained through all open loading doors.