MACRO- AND MICRO-EVALUATION OF AIR INTAKE - A DEMONSTRATION OF THE NEED FOR MORE OPTIMAL TOOLS

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1 MACRO- AND MICRO-EVALUATION OF AIR INTAKE - A DEMONSTRATION OF THE NEED FOR MORE OPTIMAL TOOLS F Frydenlund, EN Haugen *, C Ahlén, I Bryn, H Davidsen, SO Hanssen and GT Møgedal SINTEF Energy Research, Trondheim, Norway SINTEF Unimed, Trondheim, Norway Erichsen & Horgen A/S, Oslo, Norway Vest-Consult A/S, Bergen, Norway NTNU Dept of Refrigeration and Air Conditioning, Trondheim, Norway ABSTRACT This paper describes systematic parallel studies of hygiene and microbiological status of air intakes and ventilation systems. Our approach was to perform separate microbiological and hygienic studies and to find a common evaluation for the results from both methods. The aim was to identify potential risk ventilation systems for indoor air contamination. From these ventilation systems, were potential risk systems identified from the hygienic method and from the microbiological method. We found a clear relation between the microbiologic and the hygienic conditions. A good hygienic factor compares to a good microbial factor; i.e. dry and clean intakes are less likely to be microbially contaminated. Bad hygienic factors were seen both with and without microbiological contamination, but the method seems to identify potential problems, which could be confirmed by a microbiological study. Ventilation systems, without such confirmation, may avoid future problems if they improve satisfactorily the hygienic factor. INDEX TERMS Humidity and, microbiology, air intake, field experiments INTRODUCTION Air intakes are the initial components of ventilation systems. The design is a compromise between the architect, the civil engineer and the HVAC engineer. The air intake is a place where and contaminants easily meet, which may lead to unwanted consequences for the ventilation system as well as for the users. This paper describes systematic parallel studies of hygiene and microbiological status of air intakes in an aim to develop a method to identify potential risk ventilation systems for indoor air contamination. METHODS This combined study includes air intakes and ventilation systems. One of the goals was to identify a possible connection between the microbiological and the hygienic parameters. The microbiological tool includes viable microbiological samplings aiming to demonstrate the microbial flora composition as compared between outdoor air and air intakes Air samples of viable microbial flora were collected at the: Intake area between the inlet grid and the filters Main plant area between the filter and the fan User area in rooms supplied with air by this ventilation system * Contact author elisabeth.haugen@sintef.no

2 Samples were collected using The Biotest RCS Centrifugal Air Sampler. The Sampling volume was liters. Tryptic Soy Agar was used for determination of total airborne microbial count, and Rose Bengal Agar for selection of moulds and yeasts. Incubation temperatures were C and C (Pasanen, Reponen and Kalliokoski ) (Ahlén ) (Ahlén and Haugen ). Evaluation of microbial flora is based on flora composition and not on numbers (Ahlén, ). Each agar strip was semi-quantified (few, moderate, rich), and specified within three levels: Specific dominance for moderate or rich growth of one genera, at incubation C, and thermotolerant, if genera was found at incubation C. Absence of a specific dominance or thermotolerant activity, was specified as a normal flora. In an aim to present the microbiological results in accordance to be able to compare the results with the hygienic data, a qualified evaluation of the flora composition were done. This evaluation was based on our experience from ten years of field studies all over Norway. The microbiological status was separated into a scale from to, where was good (normal flora) and very contaminated. The hygienic method tries to reveal the handling of and contamination, and also the history of the ventilation system (Lysne, Ahlén and Stang ). We then focused on hygienic factors and tried to quantify them in a scale from -, where are good and very bad: the condition before and after the drainage contamination the level of contamination porosity/sponginess the surfaces and the possibility of unwanted storing outdoor intake area of ventilation plant porous surfaces? filter contaminants? air flow before drainage after Figure sketch of intake area Figure illustrates some of the items in Table. We differ findings between before and after drainage. Sign of is seriously worse after drainage than before. As a simplified tool we defined a total hygienic factor based on these three factors: hyg.fac. =. * sqrt( * contaminants * porosity) () What s behind equation ()? We multiply the factors so that a combination of bad factors gives a high total factor. Using the square root to get higher gradient at low levels than high levels, and using factor. to scale it from to.

3 Table description of the hygienic factors hyg contaminants porosity fac before dry & no sign of clean and dustless hard & smooth drainage probably some snow some dust smooth w/corrosion corrosion & sign of moist. dust & dry leaves smooth concrete sign (or report) of lot of m. dirt normal concrete magazined a lot of dust coarse concrete undrained water insects porous contaminants after corrosion & sign of moist. debris porous ceiling drainage magazined it must be compost porous floor sign (or report) of lot of m. compost look-a-like porous walls undrained water a lot of compost every surface porous RESULTS From the hygienic tool evaluation, of the ventilation systems were identified as potential risk systems. The microbiological analyses showed significantly altered flora composition in the intake of of the ventilation systems; i.e only ~ % as compared to the hygienic evaluation. Of these, nine were concluded as highly potential risk ventilation systems in that also thermotolerant moulds were identified. Risk estimate If we choose a value to divide the results into good & bad factors we could use crosstabulation. If we use a value of. we get this table (some differences from results above): Table cross-tabulation between the microbial- and hygienic factor Hygienic factor Total good < bad >= Microbia good < l factor bad >= Total By Table we can calculate the probability to find good microbiology: if the hygiene is good :. and if the hygiene is bad :. It s only ventilation systems so the % confidence intervals are wide. Microbiology versus the hygienic factors Figure shows a chart where the microbiological- and the factor are plotted for every of the ventilation systems. A low factor is good, and a high factor is worse. We find nearly all the points inside the upper triangle so it s some connection. A low factor does correspond to low microbial problems. But for a high factor we find both normal and problematic microbiology.

4 Moisture factor High High with problems Low Figure Moisture factor Figure shows other hygienic factors in combination with the microbiological factor. These factors look more scattered than the factor. But also here we find a kind of triangle in the plot. And we could also draw a straight line to indicate a tendency. Contaminant factor Porous factor Figure Contaminant and porous factors Figure shows a chart where the microbiological- and the hygienic factor are plotted for every of the ventilation systems. The hygienic factor is a combination of the, contaminant and porous factors see eq. (). The symbols indicate levels of. Naturally we also here find the ventilation systems in the upper left triangle.

5 Hygienic factor little much Figure Hygienic and microbiological factors - Figure shows the same as figure, but the ventilation systems are grouped by age. Here we can say that the newest ventilation systems have the best hygienic factor. age Hygienic factor - years - years above years Figure Hygienic and microbiological factors - age of ventilation system DISCUSSION This study is performed in an aim to develop a tool for rapid diagnosis of risk ventilation systems regarding comfort ventilation. The study included evaluation of two separate evaluations microbiology and hygiene which were to be used together in this new tool. The results from this first study show a potential for the tool to be developed. A good hygienic factor compares to a good microbial factor; i.e. dry and clean intakes are less likely to be microbiologically contaminated. The risk estimate tells the same story. The five worst microbiologically contaminated intakes are all or more on the hygienic scale, indicating microbial consequences of high humidity. So far, the combination of the two methods has strengthened the experience from our field studies in problem buildings.

6 Figure show that some ventilation systems have high humidity levels without corresponding microbial contamination. The mechanisms responsible for this is not known so far, but it looks like the levels of the hygienic factor do limit the microbiological factor. We may say that the hygienic factors indicate the microbiological potential, but not the actual microbiologically result. We have only studied ventilation systems and there is some bias in the selection of the ventilation systems. The selection is dominated by old&bad systems and new&good systems. This could be a drawback with this study. CONCLUSION AND IMPLICATIONS Bad hygienic conditions are likely to render microbial consequences. In this study, a strong connection between the microbial contamination and the bad hygienic conditions were expressed. We found no biological contaminated systems with wellmaintained and clean air intakes and ventilation systems. Hygienic evaluations may well be used for risk assessments and contamination of air intake. For proper exposure risk evaluation, additive samplings such as microbiological assessments will be of importance. If no microbial problem is pointed out, a future problem could be avoided by improving the hygienic factor. ACKNOWLEDGEMENTS This study was financed by The Research Council of Norway (NFR) and the companies: Camfil Farr, Auranor and Wide REFERENCES Pasanen AL, Reponen T, and Kalliokoski P.. Seasonal variation of fungal spore levels in indoor and outdoor air in subarctic Climate. Proceedings of the th International Conference on Indoor Air Quality and Climate - Indoor Air ', Vol.,, pp -. Ahlén C,. Determination of Viable microbes in indoor Air - What do we gain? Proceedings of the International Symposium on Indoor Air Quality in Practice -Moisture and Cold Climate Solutions. pp -. Ahlén C, and Haugen EN.. HVAC-induced alterations in microbial flora of indoor air a potential for increased pathogenity of microbes? Proceedings of the th International Conference on Indoor Air Quality and Climate Indoor Air, Vol.,, pp -. Frydenlund F, Haugen EN, Kristiansen O, Ahlén C, and Hansen SO.. Study of used filters under dry and wet conditions. Proceedings of the th International Conference on Indoor Air Quality and Climate Indoor Air ', Vol.,, pp -. Ahlén C, Haugen EN, and Frydenlund F. et al. Composting in ventilation filters - A possible key to altered thermotolerance in microbial flora of indoor air. Proceedings of the th International Conference on Indoor Air Quality and Climate Indoor Air, Vol.,, pp-. Lysne HN, Ahlén C, Stang J, Kristiansen O, Haugen EN, Frydenlund F, and Hansen SO.. Hygienic conditions in ventilation systems and possible impact on indoor air microbial flora. Proceedings of the th International Conference on Indoor Air Quality and Climate Indoor Air, Vol.,, pp -.