Sump additives as a source of bioaerosols in a school building

An investigation was launched following complaints of poor air quality and building-related illness in a public elementary school. Occlusion of air intakes put the building under negative pressure and caused vents from a below-ground sump to become air intakes. Outside air drawn through the sump pit traveled into the adjacent main air handling unit and was disseminated throughout the building. Sump additives introduced in an attempt to counteract foul odors contained spores of Bacillus species, which appeared as bioaerosols throughout the school. Viable microbial sampling identified B subtilis, B cereus, and B licheniformis in the sump room and classrooms at levels as high as 760 colony forming units/m3 (CFU/m3). Concentrations of CO2 in classrooms were 1250 ppm, indicating inadequate makeup air. Remediation was accomplished by opening the air intakes, isolating the sump room from the air handling system, venting the sump to the outside, and flushing the sump with fresh water on a regular basis.