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. 2020 Sep 19;14(3):793–811. doi: 10.1007/s12273-020-0693-3

Dust accumulated fungi in air-conditioning system: Findings based on field and laboratory experiments

Zhijian Liu 1,✉, Yuzhu Deng 1, Shengyuan Ma 1, Bao-Jie He 2,✉, Guoqing Cao 3
PMCID: PMC7501501  PMID: 32983398

Abstract

This study analyzes the growth and reproduction of dust accumulated fungi (DAF) in an air-conditioning system based on field measurement and molecular biology, laboratory experiment and prediction modelling. The field measurement was conducted to collect dust in filter screen, surface cooler and air supply duct of two air handling units (AHUs). The results indicate that dust volume and fungal number in two AHUs generally met the hygienic specification of public buildings, but the cleansing did not fulfil requirements. High-throughput sequencing was conducted, revealing that the dominant fungal species were Alternaria_betae-kenyensis, Cladosporium_delicatulum, Aspergillus_sydowii, Verticillium_dahliae. Laboratory experiment was conducted to analyze the impact of several factors (e.g. growth time, temperature, relative humidity, duct material) and their combination on the DAF growth. The results indicate that fungal growth increased with time, peaking at 4 days or 5 days. Higher relative humidity or temperature was conducive to fungal growth. The orthogonal experiment revealed that the condition of “antibacterial composite, 22 ± 1 °C and 45%–55% RH” had the strongest inhibiting impact on fungal growth. Logistic model, Gompertz model and square-root model were further developed to predict the fungal growth under different conditions. The results show that the Logistic model had high feasibility and accuracy, the Gompertz model was feasible with lower accuracy and the square-root model was feasible with high accuracy. Overall, this study facilitates the understanding of the DAF growth in air-conditioning ducts, which is important for real-time prediction and timely control of the fungal contamination.

Keywords: dust accumulated fungi, high-throughput sequencing, air supply duct, duct material, orthogonal experiment, fungal growth prediction

Acknowledgements

This work was supported by the National Natural Science Foundation of China (No. 51708211, No. 41977368).

Contributor Information

Zhijian Liu, Email: zhijianliu@ncepu.edu.cn.

Bao-Jie He, Email: baojie.he@unsw.edu.au.

References

  1. Bakó-Biró Z, Wargocki P, Weschler CJ, Fanger PO. Effects of pollution from personal computers on perceived air quality, SBS symptoms and productivity in offices. Indoor Air. 2004;14:178–187. doi: 10.1111/j.1600-0668.2004.00218.x. [DOI] [PubMed] [Google Scholar]
  2. Batterman S, Burge H. HVAC systems as emission sources affecting indoor air quality: A critical review. HVAC&R Research. 1995;1:61–78. [Google Scholar]
  3. Belanger K, Beckett W, Triche E, Bracken MB, Holford T, et al. Symptoms of wheeze and persistent cough in the first year of life: Associations with indoor allergens, air contaminants, and maternal history of asthma. American Journal of Epidemiology. 2003;158:195–202. doi: 10.1093/aje/kwg148. [DOI] [PubMed] [Google Scholar]
  4. Bluyssen PM, Cox C, Seppänen O, de Oliveira Fernandes E, Clausen G, et al. Why, when and how do HVAC-systems pollute the indoor environment and what to do about it? the European AIRLESS project. Building and Environment. 2003;38:209–225. [Google Scholar]
  5. Chang JCS, Foarde KK, VanOsdell DW. Assessment of fungal (Penicillium chrysogenum) growth on three HVAC duct materials. Environment International. 1996;22:425–431. [Google Scholar]
  6. Gibson AM, Bratchell N, Roberts TA. The effect of sodium chloride and temperature on the rate and extent of growth of Clostridium botulinum type A in pasteurized pork slurry. Journal of Applied Bacteriology. 1987;62:479–490. doi: 10.1111/j.1365-2672.1987.tb02680.x. [DOI] [PubMed] [Google Scholar]
  7. Gupta S, Khare M, Goyal R. Sick building syndrome—A case study in a multistory centrally air-conditioned building in the Delhi City. Building and Environment. 2007;42:2797–2809. [Google Scholar]
  8. Kanaan M, Ghaddar N, Ghali K. Localized air-conditioning with upper-room UVGI to reduce airborne bacteria cross-infection. Building Simulation. 2016;9:63–74. [Google Scholar]
  9. Kelley ST, Theisen U, Angenent LT, St Amand A, Pace NR. Molecular analysis of shower curtain biofilm microbes. Applied and Environmental Microbiology. 2004;70:4187–4192. doi: 10.1128/AEM.70.7.4187-4192.2004. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Li A, Liu Z, Zhu X, Liu Y, Wang Q. The effect of air-conditioning parameters and deposition dust on microbial growth in supply air ducts. Energy and Buildings. 2010;42:449–454. [Google Scholar]
  11. Li A, Chen X, Gu C, Gao R, Hu Z. Prediction of particle deposition in rectangular ventilation ducts. International Journal of Ventilation. 2012;11:69–78. [Google Scholar]
  12. Li A, Liu Z, Liu Y, Xu X, Pu Y. Experimental study on microorganism ecological distribution and contamination mechanism in supply air ducts. Energy and Buildings. 2012;47:497–505. [Google Scholar]
  13. Liu Y, Nie Y, Zhang L, Tu F. Impact of cleaning of air conditioning duct systems on indoor inhalable particles and microorganisms. Journal of HV&AC. 2005;35(2):77–95. [Google Scholar]
  14. Liu Z, Zhu Z, Zhu Y, Xu W, Li H. Investigation of dust loading and culturable microorganisms of HVAC systems in 24 office buildings in Beijing. Energy and Buildings. 2015;103:166–174. [Google Scholar]
  15. Liu G, Xiao M, Zhang X, Gal C, Chen X, et al. A review of air filtration technologies for sustainable and healthy building ventilation. Sustainable Cities and Society. 2017;32:375–396. [Google Scholar]
  16. Liu Z, Ma S, Cao G, Meng C, He B. Distribution characteristics, growth, reproduction and transmission modes and control strategies for microbial contamination in HVAC systems: A literature review. Energy and Buildings. 2018;177:77–95. [Google Scholar]
  17. Liu Z, Yin H, Ma S, Wei B, Jensen B, Cao G. Effect of environmental parameters on culturability and viability of dust accumulated fungi in different HVAC segments. Sustainable Cities and Society. 2019;48:101538. [Google Scholar]
  18. Lu Z, Zhang J, Cao D, Huang X. Testing and analysis for microbes and particles in central air conditioning systems of public buildings. Journal of HV&AC. 2007;37(1):103–107. [Google Scholar]
  19. Maddalena R, Mendell MJ, Eliseeva K, Chan WR, Sullivan DP, et al. Effects of ventilation rate per person and per floor area on perceived air quality, sick building syndrome symptoms, and decision-making. Indoor Air. 2015;25:362–370. doi: 10.1111/ina.12149. [DOI] [PubMed] [Google Scholar]
  20. McDonald K, Sun D-W. Predictive food microbiology for the meat industry: a review. International Journal of Food Microbiology. 1999;52:1–27. doi: 10.1016/s0168-1605(99)00126-9. [DOI] [PubMed] [Google Scholar]
  21. McMeekin TA, Chandler RE, Doe PE, Garland CD, Olley J, et al. Model for combined effect of temperature and salt concentration/water activity on the growth rate of Staphylococcus xylosus. Journal of Applied Bacteriology. 1987;62:543–550. doi: 10.1111/j.1365-2672.1987.tb02687.x. [DOI] [PubMed] [Google Scholar]
  22. McMeekin TA, Olley J, Ratkowsky DA, Ross T. Predictive microbiology: towards the interface and beyond. International Journal of Food Microbiology. 2002;73:395–407. doi: 10.1016/s0168-1605(01)00663-8. [DOI] [PubMed] [Google Scholar]
  23. Mendell MJ, Lei-Gomez Q, Mirer A, Seppanen O, Brunner G. Risk Factors in Heating, Ventilating, and Air-Conditioning Systemsfor Occupant Symptoms in US Office Buildings: The EPA BASE Study. Berkeley, CA USA: Ernest Orlando Lawrence Berkeley NationalLaboratory; 2006. [Google Scholar]
  24. Mendell MJ, Mirer AG, Cheung K, Tong M, Douwes J. Respiratory and allergic health effects of dampness, mold, and dampness-related agents: a review of the epidemiologic evidence. Environmental Health Perspectives. 2011;119:748–756. doi: 10.1289/ehp.1002410. [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. Meng C, Wang Q, Song Y, Cao Y, Zhao N, Shi Y. Experimental study on both cleaning effect and motion performance of the duct-cleaning robot. Sustainable Cities and Society. 2015;14:64–69. [Google Scholar]
  26. MOH (2012a). Hygienic specification of central air conditioning ventilation system in public buildings. Ministry of Health of China. (in Chinese)
  27. MOH (2012b). Specification for cleaning and disinfection of central air conditioning ventilation system in public buildings. Ministry of Health of China. (in Chinese)
  28. Noris F, Siegel JA, Kinney KA. Biological and metal contaminants in HVAC filter dust. ASHRAE Transactions. 2009;115(2):484–491. [Google Scholar]
  29. Oladokun MO, Ali M, Osman SB, Lin Z. Indoor mould growth prediction using coupled computational fluid dynamics and mould growth model. Building Simulation. 2017;10:551–562. [Google Scholar]
  30. Pakarinen J, Hyvärinen A, Salkinoja-Salonen M, Laitinen S, Nevalainen A, et al. Predominance of Gram-positive bacteria in house dust in the low-allergy risk Russian Karelia. Environmental Microbiology. 2008;10:3317–3325. doi: 10.1111/j.1462-2920.2008.01723.x. [DOI] [PubMed] [Google Scholar]
  31. Pitkäranta M, Meklin T, Hyvärinen A, Paulin L, Auvinen P, et al. Analysis of fungal flora in indoor dust by ribosomal DNA sequence analysis, quantitative PCR, and culture. Applied and Environmental Microbiology. 2008;74:233–244. doi: 10.1128/AEM.00692-07. [DOI] [PMC free article] [PubMed] [Google Scholar]
  32. Price DL, Simmons RB, Ezeonu IM, Crow SA, Ahearn DG. Colonization of fiberglass insulation used in heating, ventilation and air conditioning systems. Journal of Industrial Microbiology. 1994;13:154–158. [Google Scholar]
  33. Qudiesat K, Abu-Elteen K, Elkarmi A, Hamad M, Abussaud M. Assessment of airborne pathogens in healthcare settings. African Journal of Microbiology Research. 2009;3(2):066–076. [Google Scholar]
  34. Ratkowsky DA, Olley J, McMeekin TA, Ball A. Relationship between temperature and growth rate of bacterial cultures. Journal of Bacteriology. 1982;149:1–5. doi: 10.1128/jb.149.1.1-5.1982. [DOI] [PMC free article] [PubMed] [Google Scholar]
  35. Rintala H, Pitkäranta M, Toivola M, Paulin L, Nevalainen A. Diversity and seasonal dynamics of bacterial community in indoor environment. BMC Microbiology. 2008;8:56. doi: 10.1186/1471-2180-8-56. [DOI] [PMC free article] [PubMed] [Google Scholar]
  36. Ross T. Indices for performance evaluation of predictive models in food microbiology. Journal of Applied Bacteriology. 1996;81:501–508. doi: 10.1111/j.1365-2672.1996.tb03539.x. [DOI] [PubMed] [Google Scholar]
  37. Satish U, Mendell MJ, Shekhar K, Hotchi T, Sullivan D, et al. Is CO2 an indoor pollutant? Direct effects of low-to-moderate CO2 Concentrations on human decision-making performance. Environmental Health Perspectives. 2012;120:1671–1677. doi: 10.1289/ehp.1104789. [DOI] [PMC free article] [PubMed] [Google Scholar]
  38. Seppänen O, Fisk WJ. Association of ventilation system type with SBS symptoms in office workers. Indoor Air. 2002;12:98–112. doi: 10.1034/j.1600-0668.2002.01111.x. [DOI] [PubMed] [Google Scholar]
  39. Seppänen O. Ventilation strategies for good indoor air quality and energy efficiency. International Journal of Ventilation. 2008;6:297–306. [Google Scholar]
  40. Toivola M, Alm S, Reponen T, Kolari S, Nevalainen A. Personal exposures and microenvironmental concentrations of particles and bioaerosols. Journal of Environmental Monitoring. 2002;4:166–174. doi: 10.1039/b108682k. [DOI] [PubMed] [Google Scholar]
  41. Wang C (2016). Study on the microorganism contamination and the effect of hygrothermal response in air handling unit. Master Thesis, Dalian University of Technology, China. (in Chinese)
  42. Whiting RC, Buchanan RL. A classification of models in predictive microbiology—A reply to KR Davey. Food Microbiology. 1993;10:175–177. [Google Scholar]
  43. Wilson SC, Palmatier RN, Andriychuk LA, Martin JM, Jumper CA, et al. Mold contamination and air handling units. Journal of Occupational and Environmental Hygiene. 2007;4:483–491. doi: 10.1080/15459620701389909. [DOI] [PubMed] [Google Scholar]
  44. Xu R (2013). Species identification and thermal response analysis of microbial contaminants in accumulated dust in air-conditioned wind systems. Master Thesis, Zhongkai University of Agriculture and Engineering, China. (in Chinese)
  45. Yu XH, Che FX. Modern Air Microbiology and Technology of Sampling, Inspection. Beijing: Military Medical Press; 1998. [Google Scholar]
  46. Zhou Q, Gao T. Environmental Engineering Microbiology. 2nd end. Beijing: Higher Education Press; 2000. [Google Scholar]
  47. Zhu X (2009). Effect of air conditioning parameters on microbial growth in dust accumulated in supply air duct. Master Thesis, Xi’an University of Architecture and Technology, China. (in Chinese)

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