Pump-rooms and other enclosed spaces normally entered which
are not covered by 12.1.1 shall
be fitted with mechanical ventilation systems, capable of being controlled
from outside such spaces and complying with the requirements of 12.1.3, except that the capacity shall
not be less than 20 changes of air per hour, based upon the total
volume of the space. Provision shall be made to ventilate such spaces
prior to personnel entering.