Balancing air flow in ventilating duct systems.

The paper is concerned with the procedure for regulating or balancing a ventilation· system, so as to ensure that each outlet supplies or extracts its proper quantity. It deals with methods, organisation instrumentation and recording of results; it also discusses the accuracy required and attainable in ordinary practice. The advocated method of regulating consists of balancing the proportions of air flow at the junctions of a system, dealt with in a routine order, followed by the adjustment of the complete system to design volume by a final setting at the fan. The main discussion is related to low-velocity systems, but the extension of the method to high velocity induction systems is also covered. The paper deals with aspects of design for air handling plant and air ducting that is required to facilitate the regulation of systems to achieve design performance. The paper does not deal with the performance of equipment for heating, cooling, filtering or humidifying the air, nor with any aspect of noise measurement and control.