MVOC EMISSIONS FROM FUNGI IN HVAC SYSTEM

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1 MVOC EMISSIONS FROM FUNGI IN HVAC SYSTEM JS Park * and K Ikeda Dept. Of Architectural Hygiene Engineering and Housing, National Institute of Public Health, Japan ABSTRACT The purpose of this research was to investigate MVOC emissions from microorganisms in HVAC systems, and also to survey their effect on indoor air quality. MVOC emissions from fungi sampled in HVAC systems were analyzed in the laboratory. 2-methyl-2-Propanol, 2-Pentanone, methyl isobutyl Ketone and others MVOC were emitted from Cladosporium, Aspergillus, Penicillium and Alternaria which were detected in HVAC systems of five buildings. MVOC emission rates of four species were greatly varied according to species, though some MVOCs were emitted from all species. And it was found from the field measurement that MVOC thought to be from fungi, such as 2-methyl-1-Propanol, 2-Pentanone and methyl isobutyl ketone, were emitted by some HVAC systems. For these results, it is suggested that MVOC emissions from fungi in HVAC system became one of the indoor pollution sources. INDEX TERMS MVOC, Fungi, HVAC System, Office building, Indoor Air Quality INTRODUCTION Components of HVAC system are essential parts in maintaining good indoor air quality in most modern buildings. Some systems, however, pollute the handling air considerably due to improper maintenance (Bluyssen et al., 2000, Bluyssen, et al., 1999). Particles and microorganisms deposit and accumulate in filters, duct systems, heat exchangers, coils and humidifiers during using time of the system (Nathanson, 1996). The polluted components contribute to indoor air pollution by emitting several pollutants to indoor, which is the opposite what they have planed to do. Microorganisms, particularly fungi, emit microbial volatile organic compounds (MVOCs) when they grow, and also produce allergens and toxins that may harm the health of occupants (Horner et al., 1999 and Kemp et al., 1995). The fungal contamination in HVAC components may be a result from poor maintenance of HVAC system. The overall goal of this research is to study fungal contamination in HVAC systems, and to develop strategies, standards and guidelines for the proper maintenance of the systems. This study aims to characterize MVOC emissions in HVAC systems due to fungal growth. METHODS Field Measurements Five office buildings located in urban area were selected to investigate the fungal contamination in HVAC system. Its systems have operated during 10 years or more since they had been * Contact author jpark@iph.go.jp 335

2 installed in buildings. Volatile organic compounds (VOCs) and spores of the fungi were sampled in HVAC system, when it was usually operated (Fig.1). VOCs were sampled at five components using charcoal samplers (sampling rate at 0.5ml/min, 60 minutes). After completing sampling, the samplers were analyzed at the laboratory by gas chromatography/ mass selective detector (GC/MSD). VOCs were extracted with 2ml carbon disulfide from the sampler by shaking, and then quantified by GC/MSD using SIM mode. Spores were sampled at both the supply air and the room using bioaerosol samplers with 100L sampling volume. In order to identify fungal species, the sampled spores were grown on potato dextrose agar (PDA) with 0.2% chloramphenicol. The identified species were cultured in the laboratory to measure MVOC emissions. All cultures were identified to species level. O.A OA SA S.A Supply Duct Filter Unit humidifier EA MA Mixing chamber HC CC Room IA E.A R.A Return Duct Figure 1. VOC and fungi sampling in HVAC system and Building (Fungi only for EA and IA) Sampling MVOC Emissions from fungi Cladosporium, Aspergillus, Penicillium and Alternaria, which were obtained from five buildings, were independently inoculated to five PDA plates (100mm diameter). Five plates were loaded into an Andersen type low volume sampler, stainless steel that was used as small chamber. The chamber was supplied with chemically pure, HEPA filtered air at 25 and 70% RH. Air samples were taken during 7 days after inoculation. Five plates temporarily removed to count colony diameters at every day. Two solid adsorbents, charcoal and Tenax-TA, were used at MVOCs sampling in order to compare the sampling performance. Table 1 shows the results of sampling performance tests. Table 1. Results of MVOC sampling performance tests in all species Adsorbents and extraction methods Compounds Charcoal Tenax-TA Extracted with CS 2 Thermal desorption Extracted with CH 3 OH 2-methyl-1-Propanol O O O 2-Pentanone O O O 3-methyl-1-Butanol O O O 2-methyl-1-Butanol O O O Methyl Isobutyl Ketone O O O 1-Octen-3ol O O O Others O O 336

3 Two solid adsorbents are capable of sampling MVOC emissions from four species, and also there was no obvious difference at the sampling rates of each compound. From these results, it was confirmed that field results sampled by charcoal adsorbent could be compared with MVOC emissions results. RESULTS Cladosporium, Penicillium, Aspergillus, Fusarium, Alternaria and Yeast were detected in the supply air (Table 2). Its colony concentrations were ranged from non-detected to 340 cfu/m 3. The most commonly detected species were Cladosporium, Penicillium and Aspergillus. Their concentrations were over 60 percents or more of total cfu concentrations in most buildings. There was no direct relation in cfu concentrations between the indoor air and the supply air. Even though some of fungi species were simultaneously encountered in the indoor air and the supply air, its cfu concentrations were greatly different. In addition, five buildings showed a unique cfu concentration distribution in not only the indoor air but also the supply air. The relative amounts of 6 MVOCs emitted from 4 species are shown in Table 3. Total MVOC emission rates were calculated using TIC peak areas, which were assumed to equivalent to toluene. Table 2. CFU concentrations of fungi species in the supply air and the indoor air* Buildings [CFU/m 3 ] Fungi S K F(3F) N Y(5F) S I S I S I S I S I Cladosporium Penicillium Aspergillus Fusarium Yeast Others * S: Supply air, I: Indoor air Table. 3 shows the results of MVOC emissions tests Compounds Cl. Pen. Asp. Al. Total MVOC emissions [ug/7days]* Individual compounds [%] 2-methyl-1-Propanol 2-Pentanone 3-methyl-1-Butanol 2-methyl-1-Butanol Methyl Isobutyl Ketone 1-Octen-3ol Others N.D. 5.9 * Quantified values using equivalent to toluene. N.D

4 Aspergillus produced the greatest MVOC emission rate in 7 days, whereas the other three species showed about 10 ug/7days or below. MVOC emission rates of four species were greatly varied according to species, though some MVOCs such as 2-Pentanone, 3-methyl-1-Butanol and 2-methyl-1-Butanol, were emitted from all species. The amount of 2-methyl-1-Propanol in Alternaria was about the half of total MVOC emission amount. Total MVOC concentration[ug/m 3 ] OA MA SA EA IA NO NO NO OA MA SA EA IA OA MA SA EA IA OA MA SA EA IA OA MA SA EA IA OA MA SA EA IA S K F(3F) N Y(4F) Buildings Figure 2. Total MVOC concentrations in HVAC systems (NO: none data, OA: outdoor air intake, MA: mixing air, SA: supply air in room, EA: end of supply air, IA: indoor air of the room) Concentration [ug/m 3 ] Octan-3ol Methyl Isobutyl Ketone 2-Pentanone 2-methyl-1-Propanol 0 S K F(3F) N Y(4F) Buildings Figure 3. MVOC concentrations in the end of supply air (EA) 338

5 Several MVOCs, which were identified in emissions tests, were detected in HVAC systems. Total MVOC concentrations were changed between locations as well as buildings, though its levels were very low (Fig. 2). Total MVOC concentrations generally increased from outdoor air through to supply air after filters, coils and humidifiers, and decreased in the room (IA). The highest concentration in HVAC systems occurred in the supply air ducts (SA) or the end of supply air (EA). 2-methyl-1-Propanol, 2-Pentanone and methyl isobutyl ketone, which are considered to be emitted from Cladosporium, were found in thew supply air of Y building (Fig. 3). MVOCs emitted from Penicillium and Aspergillus were found in F building. But, all MVOCs, which were considered to be emitted from the obtained species of supply air, were not detected in the end of supply air (EA). And MVOC concentrations of the indoor air were not corresponding with those of the supply air. DISCUSSION The spore sampling results illustrate that the fungi of indoor air were not directly related to HVAC systems. Every building presents a unique concentration distributions in both the supply air and the room. There was no typical behavior that related to the fungi of indoor air. Even though there is an internal source of several fungi in the room, some of the indoor air fungi clearly occur from HVAC system. Most fungi of the supply air are considered to be introduced through HVAC system from outdoor air, dispersion of the fungi deposited in HVAC components, because of improper filtering and maintenance. And some spores are introduced from the fungi that grow in HVAC components. But its is still unclear where, how and when the fungi grow in the components. Six MVOCs were detected from four species (Table 3). The presence and relative ratio of the MVOCs differed among the species, though four MVOCs were emitted from all species. These MVOC patterns can be used to assess the fungal growth in HVAC systems. It is necessary to understand, however, that the MVOCs profile presented in Table 3 is one part of several MVOC emission patterns, because it will be changed according to fungal growth stage, environmental conditions and nutrition. Furthermore, MVOC emissions patterns in Table 3 do not present the emissions from all genera of four species, because all fungi were obtained from field measurements and also identified to species level in this study. The characteristics of MVOC emission patterns depending on the fungal growth stage, environmental conditions, nutrition, etc. will play a very important role to study the effect of MVOC emissions on indoor air quality, especially sensory pollution. Although MVOC concentrations were very low levels, MVOCs were detected in HVAC components of all buildings. Total MVOC concentrations generally increased from outdoor air to the supply air, and decreased in the room. The highest concentration in HVAC systems mainly occurred in the supply air ducts and the end of the supply air. The supply air of Y and F buildings included MVOCs that were considered to be emitted from Cladosporium, penicillium and aspergillus. These results indicate that some MVOCs were emitted from HVAC components, and then were introduced into the room by the handling air. But, MVOC patterns and ratios detected in the supply air were not completely corresponding to emission profiles of each species, and also all MVOCs of the sampled fungi were not found in the supply air. Furthermore, it was not considered that all spores obtained from the supply air were produced from the growing fungi in components of each building. Therefore, the process of the fungal contamination in HVAC 339

6 components and the characterization of MVOC emissions in HVAC environmental conditions should be investigated. ACKNOWLEDGEMENTS This study was supported by coordination funds for promoting science and technology from the Science and Technology Agency of Japan. REFERENCES Kemp S J, et al., Growth of microorganisms HVAC filters under controlled temperature and humidity conditions, ASHRAE trans. pp.1-12 Nathanson T., Microbial and HVAC system operation and maintenance in office buildings, Indoor Air 96 The 7 th International Conference on Indoor Air Quality and Climate, Vol.2, pp Philomena M. Bluyssen, et al., Why, When and How do HVAC-System pollute?, Characterisation of HVAC System related Pollution, Proceedings of Healthy Buildings 2000, pp Philomena M. Bluyssen, et al., AIRLESS, A European Project on HVAC Systems: Project Programme AndCurrent Status, Indoor Air 99 The 8 th International Conference on Indoor Air Quality and Climate, Vol.1, pp W E Horner, P R Morey and M S Blak, MVOC and VOC Emission patterns from Multiple Strains of Indoor Fungi, Indoor Air 99 The 8 th International Conference on Indoor Air Quality and Climate, Vol.1, pp