Abstract
Optimal placement of outdoor air intakes and exhaust outlets is a source control measure to avoid the degradation of air quality at the air intakes. Re-entrainment is an occasional air pollution instance that happens if pollutants in the exhaust air stream, after being discharged to outdoors, are transferred back to outdoor air intake location due to unfavorable meteorological conditions and inadequate positioning of the air intakes and exhaust outlets. In engineering practice, it is impractical to always conduct detailed dispersion modeling due to the complexity of airflow phenomena in the urban environments, and therefore, engineers rely on prescriptive design guidelines or simplified empirical models published in technical literature and regulation documents. Commonly, the design guidelines to avoid the re-entrainment phenomenon are for buildings with rooftop exhaust stacks, but the exhaust outlets might also be situated on the building façade. The objective of this paper is to overview the existing design guidelines for the placement of horizontal air intakes and exhaust outlets. Technical engineering literature, including international standards, codes, and guidebooks is reviewed to extract both qualitative and quantitative design guidelines relevant to the placement of air intakes and exhausts on an external wall.
Highlights
In developed countries, the inhalation of indoor air contaminants by the building occupants constitutes a significant fraction of the total personal exposure to environmental pollution during a person’s lifetime [1]
Proper consideration should be given to the correct specification of designated outdoor air intakes and exhaust outlets to minimize the risk of indoor air pollution caused by the re-entry of contaminants previously discharged from the ventilation exhaust outlet to the outdoor environment
The purpose of ventilation standards and codes is to establish a common basis for decision-making in the ventilation design process by typically setting minimum quality criteria to provide acceptable indoor air quality
Summary
The inhalation of indoor air contaminants by the building occupants constitutes a significant fraction of the total personal exposure to environmental pollution during a person’s lifetime [1]. Ventilation exhaust air re-entrainment is an episodic air pollution event which occurs when the discharged exhaust air is transported back into the building through ventilation air intakes or other openings in the building enclosure [3] and it can potentially induce indoor air quality problems from comfort issues like nuisance due to odors to re-entry of pollutants that are harmful to health [4]. Proper consideration should be given to the correct specification of designated outdoor air intakes and exhaust outlets to minimize the risk of indoor air pollution caused by the re-entry of contaminants previously discharged from the ventilation exhaust outlet to the outdoor environment
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