Section 108.437 - Pipe sizes and discharge rates for enclosed ventilation systems for rotating electrical equipment(a) The minimum pipe size for the initial charge must meet table 108.441 and the discharge of the required amount of CO2 must be completed within 2 minutes.(b) The minimum pipe size for the delayed discharge must be at least 1.25 centimeters ( 1/2 inch) standard pipe.(c) The pipe used for the initial discharge must not be used for the delayed discharge, except systems having a volume of less than 57 cubic meters (2,000 cubic feet).