Alain Perdrix

Multivariate analysis comparing microbial air content of an air-conditioned building and a naturally ventilated building over one year

Heating, ventilation and air-conditioning (HVAC) may be responsible for the production and spread of airborne microorganisms in office buildings. In order to compare airborne microbiological flora in an air-conditioned building with that in a naturally ventilated building, eight sets of measurements were made over a 1-year period. Concurrently with other environmental measurements, air samples were collected in each building, from three offices and from the outdoor air, using the Andersen single-stage sampler. Three different media were used to culture fungi, staphylococci and mesophilic bacteria. Multivariate analysis revealed a group of offices more contaminated than others, and a marked seasonal variation in fungal concentrations. A comparison of mean levels of microorganisms measured in the two buildings showed that the air microbial content was significantly higher and more variable in the naturally ventilated building than in the air-conditioned building. Moreover, in the naturally ventilated building, the interior fungal content was strongly dependent on the outdoor content, while in the air-conditioned building fungal concentrations remained constant despite significant variations measured outside. This was confirmed by a statistical comparison of the correlation coefficients between indoor and outdoor concentrations. No difference was observed regarding gaseous pollutants and temperature, but relative humidity was significantly higher in the air-conditioned building. The effect of HVAC was to prevent the intake of outdoor particles and to dilute the indoor concentrations. These results are consistent with the presence of high-efficiency filters and a steam humidifier in the HVAC system under study.

Airborne Fungal Contamination in Air-Conditioning Systems: Effect of Filtering and Humidifying Devices

The fungal contamination of air processed by an air-conditioning system can be quite high, depending on the technical features of different parts such as filtering and humidifying devices, as well as on their maintenance. The effect of filtration and humidification by sprayed water on the fungal air content was studied by analyzing the total culturable airborne fungi and four mold genera: Aspergillus, Beauveria, Cladosporium, and Penicillium. In four air-conditioning systems air samples were collected simultaneously on either side of the filters and humidifiers, using four single-stage viable particle samplers, on a malt agar chloramphenicol medium. High-efficiency filters (EU7) and lower efficiency filters (EU4)were compared, with actual efficiency calculated for every genus identified. The concentration levels measured below the high-efficiency filters were significantly lower than that measured above the filters. For the EU4 filters, the differences were not significant for Beauveria and Penicillium. F...

Contamination of air systems: 1987–88 assessment and prospects of the Grenoble intervention group

SummaryIn order to evaluate bacterial and fungal contamination, the authors used a qualitative and quantitative procedure and investigated 47 air conditioning and humidifying units.Air samples were studied using Biotest RCS biocollector (160×6 liters on 6 different selective media), whilst dust samples were analysed after spreading 10 mg onto fungal media.Selective research ofLegionella and fungi were performed using water filtrates and specific media. Even though, the most frequently identified species were quite common environmental fungi, mainlyPenicillium, Alternaria andAspergillus fumigatus (36 out of 47 collections), the health effects of intense exposure to these common moulds are not really known.Staphylococcus aureus was identified 6 times and thermophilic actinomyces species (A. candidus) once. From the quantitative analysis a significant relationship was found between some risk factors and airborne contamination. Indeed bacteria and fungi number depends on the humidifying system (steam or washer), efficiency of secondary filters, relative humidity percentage (< or >60%), installation maintenance, industrial activity and complaints of people at risk. The presence of air recycling and biocide use seems only to have an influence on fungal flora. Having determined a global risk score for each air conditioning unit, the authors underline the fact that bacterial and fungal airborne contamination increases with score. Moreover, for a global, metrological, medical and technical evaluation, a multidisciplinary approach has proved itself to be indispensable.