Which of the following is NOT a component of a dilution ventilation system?

A dilution ventilation system is designed to reduce the concentration of airborne contaminants in a space by mixing outside air with contaminated indoor air, thereby lowering the overall pollutant concentration.

A local air conditioning unit serves a different purpose; it primarily controls temperature and humidity levels in a localized area rather than functioning as part of a dilution system. In a typical dilution ventilation setup, the key components include a source of air supply to introduce fresh air into the space, a duct system to distribute this air throughout the area, and a source of air exhaust to remove the contaminated air from the space. Each of these components plays a vital role in ensuring effective dilution of contaminants.

Thus, the local air conditioning unit does not fit within the framework of a dilution ventilation system, making it the option that is not part of such a setup. Understanding the specific roles of ventilation components is crucial for anyone involved in industrial hygiene and environmental health and safety practices.