Detection and Decontamination of a Facility Contaminated with Fungi Including Stachybotrys chartarum

Ling-Ling Hung, Ph.D. US Public Health Service, Division of Federal Occupational Health, Philadelphia, PA Email:

A facility indoor environmental quality investigation was initiated in 1996 due to onset of employees' health symptoms after fifteen minutes exposure in the facility. The investigation was to determine the extent of contamination, identify the causative agents, design decontamination specifications, and develop and implement a monitoring strategy for clearance sampling.

Massive fungal growth was observed on various surfaces. Many types of microbiological samples were collected throughout this two-story facility. Very high fungal levels were detected on bulk and wipe samples (107 CFU/g and 106 CFU/in2). Three rounds of air samplings were conducted. Outdoor fungal levels were at 102 CFU/m3 with Cladosporium as the predominant fungi. However, indoor fungal levels were consistently at least 104 CFU/m3. Indoor fungal flora was dominated by Aspergillus, Penicillium, and Stachybotrys chartarum. Analytical results showed that basement, ground floor, and ductwork were contaminated.

Specifications were developed to decontaminate the facility and the ductwork. Ten percent (10%) bleach solution and OxineŽ brand of chlorine dioxide (500 ppm) was used as the disinfectant for the facility and the ductwork, respectively. Final clearance samples were taken to evaluate the effectiveness of the cleaning. Air sampling results showed that airborne fungal levels in the facility were compatible to those of outdoors (230 and 224 CFU/m3, respectively), with a similar fungal flora. Results from final clearance surface samples, taken after completion of second ductwork cleaning, showed that surface fungal burden of this facility was not different from that of a reference building.