AIRBORNE FUNGAL CONTAMINATION IN AIR-CONDITIONING SYSTEMS - EFFECT OFFILTERING AND HUMIDIFYING DEVICES

The fungal contamination of air processed by an air-conditioning syste m can be quite high, depending on the technical features of different parts such as filtering and humidifying devices, as well as on their m aintenance. The effect of filtration and humidification by sprayed wat er on the fungal air content was studied by analyzing the total cultur able airborne fungi and four mold genera:Aspergillus, Beauveria, Clado sporium, and Penicillium. In four air-conditioning systems air samples were collected simultaneously on either side of the filters and humid ifiers, using four single-stage viable particle samplers, on a malt ag ar chloramphenicol medium. High-efficiency filters (EU7) and lower eff iciency filters (EU4) were compared, with actual efficiency calculated far every genus identified. The concentration levels measured below t he high-efficiency filters were significantly lower than that measured above the filters. For the EU4 fitters, the differences were not sign ificant for Beauveria and Penicillium. For the latter a release of spo res was detected, raising the question of the growth of microorganisms within the filters. The EU7 filter efficiency (80 to 97%) was higher than that of the EU4 filters, ranging from 36 to 70% depending on the fungi. This variability between genera raises the question of how depe ndent filter efficiency is on the diameter of particles, as stated for inert particles. Finally, the concentration levels below the humidifi er were lower than above it. This was related to the low contamination of the water itself (less than 100 colony-forming units per millilite r).