Tar fumes trigger inquiry that finds source of IAQ ills at school.

Describes a case of an elementary school which suffers indoor air quality problems as a result of the application of hot coal-tar to the roof, causing major health concerns. Eight roof-mounted air handling units provided heating, ventilation and air conditioning. The space above the ceiling served as the return-air plenum. Four AHUs provided ventilation to most classrooms with variable air volume boxes controlling airflow. Outdoor air intake dampers on each AHU supplied 10% outdoor air to each wing of the school. The health problems were put down to 'odour nuisance', but recurred some months later due to hot weather. A comprehensive environmental analysis revealed high levels of carbon dioxide (600-2,000 ppm), which prompted a review of the ventilation system. It was concluded that levels of VOCs and PNAs measured in the school were normal, even in hot weather, but that existing IAQ problems were due to poor operation and balancing of the ventilation system.