ABSTRACT
The term general exhaust ventilation has acquired a specific meaning in comparison to local exhaust ventilation, and refers to the ventilation process in which the general space is constantly flushed with fresh, outdoor air. Natural ventilation is effected by natural air movement—wind and temperature differences—through wall and roof openings. Mechanical ventilation is induced by motor driven fans. Attainment of a good understanding of the character of a given ventilation problem is required before a proper basis for ventilation can be laid. In many instances it is necessary to make searching inquiry into the exact nature of the condition for which ventilation is sought, especially where thermal factors are involved and where the information sources are untrained individuals. The term, significant air currents, applied to problems in general ventilation, means—those air currents having a constant position and direction, and of such magnitude that they are measurable.
