Contaminant control has been widely used to reduce paniculate matter levels in heating, ventilating, and air-conditioning (HVAC) system airstreams and in building spaces. Contaminant control measures are often used because they are considered to be both practical and technically appropriate to the task. Typical contaminant control measures include general dilution ventilation, proper operation of HVAC systems, local exhaust ventilation, and air cleaning. General or dilution ventilation is the most popular contaminant control measure used in large office, institutional, and commercial buildings. Local exhaust ventilation can be used in special circumstances to reduce contaminant levels in buildings. Local exhaust ventilation is commonly used in office and other public-access buildings to control odors from lavatories. It is also used to control combustion and cooking by-products as well as odors from cafeteria kitchens. General or dilution ventilation is the most popular contaminant control measure used in large office, institutional, and commercial buildings.