Air quality must be maintained to ensure a healthy, comfortable environment indoors. Sources of pollution exist in both the internal and external environment. Indoor air quality is controlled for the removal of pollutants or by dilution. Ventilation plays an important role in both processes. Ventilation is defined as air, natural or mechanical means to the place. As a rule, the ventilation air from the outside air and recirculated air. Outdoor air dilution. In most cases, odor and irritation of the upper respiratory tract and eyes reason for ventilation, but not the presence of hazardous substances. The possibility of polluting substances should not be overlooked, however. ....
Reference prescribes both necessary quantities of ventilation for various types of occupancies and methods of determining the proportions of outside air and recirculated air. If the level of contaminants in outdoor air exceeds that for minimum air-quality standards, extraordinary measures beyond the scope of this text must be used. For the present discussion it will be presumed that outdoor-air quality is satisfactory for dilution purposes. Table 4-1 presents outdoor-air requirements for ventilation for three occupancy types listed in the standard. As noted in the table, much larger quantities of air are required for dilution in areas where smoking is permitted.
Ventilation imposes a significant load on heating and cooling equipment and thus is a major contribution to energy use. Space occupancies and the choice of ventilation rates should be considered carefully. For example, if smoking is permitted in part of a building but restricted in another part of the building, ventilation rates for smoking should not be assumed uniformly. Also, the prospect of filtering and cleaning air for recirculation must be examined carefully.
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