The ability of hospital ventilation systems to filter Aspergillus and other fungi following a building implosion

OBJECTIVES: To assess the ability of hospital air handling systems to filter Aspergillus, other fungi, and particles following the implosion of an adjacent building; to measure the quantity and persistence of airborne fungi and particles at varying distances during a building implosion; and to determine whether manipulating air systems based on the movement of the dust cloud would be an effective strategy for managing the impact of the implosion. DESIGN: Air sampling study. SETTING: A 976-bed teaching hospital in Baltimore, Maryland. METHODS: Single-stage impactors and particle counters were placed at outdoor sites 100, 200, and 400 m from the implosion and in five locations in the hospital: two oncology floors, the human immunodeficiency virus unit, the cardiac surgical intensive care unit, and the ophthalmology unit. Air handling systems would operate normally unless the cloud approached the hospital. RESULTS: Wind carried the bulk of the cloud away from the hospital. Aspergillus counts rose more than tenfold at outdoor locations up to 200 m from the implosion, but did not increase at 400 m. Total fungal counts rose more than sixfold at 100 and 200 m and twofold at 400 m. Similar to Aspergillus, particle counts rose several-fold following the implosion at 100 and 200 m, but did not rise at 400 m. No increases in any fungi or particles were measured at indoor locations. CONCLUSION: Reacting to the movement of the cloud was effective, because normal operation of the hospital air handling systems was able to accommodate the modest increase in Aspergillus, other fungi, and particles generated by the implosion. Aspergillus measurements were paralleled by particle counts.