HYGIENIC AND MICROBIOLOGICAL (HYGMIC) EVALUATION OF AIR INTAKE AND PLANTS TEN-YEARS-EXPERIENCE

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1 Topic B3: Control of indoor environment HYGIENIC AND MICROBIOLOGICAL (HYGMIC) EVALUATION OF AIR INTAKE AND PLANTS TEN-YEARS-EXPERIENCE Elisabeth N. HAUGEN 1,*, Monica BERNER 2, Maria J. ALONSO 1, Frode FRYDELUND 1 and Bjarne MALVIK 1 1 SINTEF Energy Research Centre, Trondheim, Norway 2 Enova SF, Trondheim, Norway * Corresponding Elisabeth.Haugen@sintef.no Keywords: Indoor air, Hygiene, Microbiology, Air Intake. SUMMARY In low energy buildings (LEB) with reduced uncontrolled leakages and tighter insulation, unwanted high humidity levels might develop, increasing the risk of mold growth. The quality of air supplied through mechanical ventilation depends on the quality of the outside air and the particle filter efficiency. However, the ducting system itself might be a risk factor. Water entering through a poorly designed air inlet may in combination with organic material and favorable temperature, result in mold growth. This paper describes our experiences gained by systematically applying a strategy based on two factors, hygiene and microbiology, to indicate the condition of air inlets and ventilation ducts and published as the HygMic method (Frydenlund 2002). The initial approach was to quantify the two indicators and compare the variation of the results with time. To develop a reliable tool for identifying potential risk ventilation systems regarding microbial indoor air contamination was the main goal. INTRODUCTION Water leaks, excessive humidity, condensation, reduced ventilation and diffusion-tight hidden constructions are often causing building-related illness and symptoms. When moisture and mold are hidden inside the construction, is it hard to identify the source of the problem. In such cases, actions to locate the site may go on for a long time if no systematic approach exists. The ventilation system is the life supporting breathing system for a building and its occupants. However, it has been shown that perceived quality of the supplied air may be inferior to the perceived quality of the outdoor air (Bluyssen et al 2001). Large internal surfaces in duct systems may both adsorb and desorb pollutants (Wargocki et al 2001). Several field studies have reported an association between indoor air quality and the cleanliness of the ventilation systems (Crandell et al 1996). Multiple respiratory symptoms are significantly related to heating, ventilation, air-conditioning and cooling (HVAC) cleanliness with a relative risk (RR)=1.8 (Sieber et al 1996). Since LEB have reduced uncontrolled air leakages and thicker insulation, good ventilation systems will be imperative. Diffusion barriers and increased potential for build-up humidity inside the construction require better strategies for controlling humidity; if not, the risk of

2 mold growth will increase. Both building construction and ventilation systems may be affected (Pasanen 1993). Infected ventilation components are unsuitable for providing fresh air. Air handling systems cleanliness importance is already recognized in the national guidelines and standards in many countries (CEN2003, FiSIAQ 2001, ASHRAE 2001, VDI ) A complete anamnesis is important for a physician in order to come up with the correct diagnosis for a sick person. When a building is characterized as "sick", the necessary historic information as is given by the patient is not easily available. In cases where occupants complain of the indoor environmental quality, e.g., reporting frequent headache, fatigue, reduced working capacity, there are no obvious signs that can explain the link between the building and the symptoms. Even to decide whether the cause is in the building construction or in the ventilation system may be difficult. Experience through more than two decades has shown that actions to cure problem buildings in most cases are based on trial and error. A strategy and tools to interpret a set of parameters that may be relevant is needed. HygMic is a method intended for evaluation of ventilation systems. It was developed ten years ago based on long term evaluation and examination of air inlets. Naturally, location and design of the air inlet may contribute to the air quality supplied to the occupants in the building. Moisture and contaminants meet at the air inlet. If they are not prevented from entering the duct system, microbial activity may be established when nutrition, humidity and temperature are favourable. A high percentage of air inlets are not designed to give full protection against rain and snow. Wind conveying precipitations through the inlet shield also transports solid material, both organic and inorganic. This may promote mold growth at the intake grate end of the ventilation ducts. Mold spores and metabolites will be distributed with the ventilation air. As long as outdoor climate influences indoor climate, weather conditions and time of the year are important. The second part of the HygMic method is the hygiene evaluation. In this context, hygiene includes the existence of general sickness or health complaints. However, cleanliness has proved to be a useful indicator when performing risk assessment. Regarding the operation of technical equipment, dirt may be an indicator for increased risk of MB pollution. METHODOLOGIES Figure 1. A frequently used design of ventilation plants showing the main components from the inlet grid and the occupants. Locations for microbial air samples are indicated by roman numerals The basic material used to establish the method, was collected by systematically studying air inlets at 30 different ventilation systems located in four cities with different climatic conditions, further called Study A. Hygienic and MB evaluations samples were taken

3 following the air from the air inlet, through ducts, filters, fans, heat exchangers, silencers until leaving the ducting system. For study A four sampling locations were chosen in each of the 30 buildings: I Outdoor air II Inlet area between the inlet grid and the filters III-IV Between the filter and the fan V Occupant areas in two rooms supplied with air from the ventilation plant Hygienic evaluation (Hyg) The hygienic status of a ventilation plant is influenced by a wide variety of parameters. Many of them are difficult to quantify. The hygienic method strives to reveal the handling of moisture and contamination and also the history of the plant (Lysne et al. 1999). Three hygienic factors were selected and quantified using a scale ranging from one to ten, where 1 is good and 10 is very bad: Moisture the condition before and after the drainage Contamination the level of contamination Porosity visually evaluation of the surfaces and the capacity for moisture storage caused by materials and dirt. Regarding the risk for microbial contamination; moisture, material porosity and contaminants are key elements. Based on an evaluation of each of those using a numeric scale for a quantitative assessment, the hygienic factor (HF) for the plant is given by the formula HF=m+ α (p+c), where α 0.14 m+0.3 (1) m= moisture factor (0-5) p= porosity factor (0-2) c= contaminants factor (0-3) α= probability factor for adverse microbial activity due to porosity and pollution (0-1), related to m. Based on (Frydenlund 2002) and (Struksnes 2003) α can be simplified by α=0.14 m Table 1: Hygiene characterization of internal cleanliness of ventilation ducts HF Rating 0-2,0 Very good hygiene - very little likelihood of adverse microbiological growth 2,1-4,0 Good hygiene - little likelihood of adverse microbial growth, but it cannot be excluded. The plant should be monitored according to specific procedures for inspection and maintenance 4,1-6,0 Intermediate hygiene - unfortunately microbial growth may occur. The plant should be monitored carefully for a period to identify possible worsening. This can be combined with microbiological sampling. Procedures for inspection, maintenance and cleaning should if possible be applied. 6,1-8,0 Poor hygiene - significant risk that the plant has or may have adverse microbiological growth. The plant should be evaluated using microbiological sampling and measures should be considered in consultation with experts in hygiene and microbiology. 8,1-10 Very poor hygiene - there is a great danger that the facility has or soon will have unwanted microbial growth. The plant should within a reasonable time be mapped using microbiological sampling, so that adequate actions may be implemented. Microbiological evaluation (Mic) For this method, airborne particles are collected by impact on agar strips from all locations. The sampling equipment was the Biotest RCS centrifugal Air Sampler (Biotest AG, Dreieich, Germany), (Lee et al., 2004a,b). The sampling rate was 40 l/min and the sampling volume

4 320 l. A Tryptic Soy Agar was used for determination of total airborne microbial count and Rose Bengal Agar as selective medium for mold and yeast. All samples were incubated at 22 C and 37 C (Pasanen 1990, Ahlen and Haugen 1996, Fydenlund and Haugen 2002). Each agar strip was semi-quantified (few, moderate, rich) and specified within three levels: Specific dominance if moderate or more colonies for one species at 22 C Thermotolerant if genera were found after incubation at 37 C Normal flora if absence of specific dominance or thermotolerant activity A normal flora in the air will be characterized by a mixture flora of various species molds, yeasts and bacteria which no species is dominant. The microbiological tool includes a semiquantitative assessment of viable microbial species. A qualified evaluation based on experience to assess microbial status was then ranged on a scale from one to ten, where one is good (normal flora) and ten is very contaminated. The HygMic method was initially developed based on study A of 30 different ventilation plants with particular attention on the air inlet design. The impact of different geographic and climatic regions was accounted by including four different cities. After evaluating the hygiene findings and the results from the microbial air samples, the most important findings were: MB contaminated plants have very often poor hygienic conditions. On the other hand we found several examples of poor hygienic condition and no significant MB contamination. Poor hygienic conditions increase the risk for MB contamination of the ventilation plant. Good hygiene conditions decrease the risk for MB contamination. Method development The first version of the method was based on results from study A of air inlets with and without a protective grid. Over time it has proven useful also for other situations involving impaired air quality and MB contamination. The method was applied on 16 ventilation plants (Struksnes 2003) with main focus on filter systems and operating modes. This work resulted in some modifications, especially regarding how to quantitate the hygienic standard. The final characterization of the hygienic factor (HF) is presented in table 2. Examples from some of the plants are given in table 2. Another interesting finding was that closing down the ventilation at night did not cause any changes in the microbiological status but for gaseous pollutants close down at night had a negative impact on the air quality. Table 2: Examples from applying the hygiene rating system Plant Moisture m Porosity p Contaminants c Probability α HF= m +α(p+c) A3 2,5 0,5 1,5 0,75 4,0 B ,5 1 7,5 C5 3 0,5 1,5 0,8 4,8 C6 5 1, ,5 Air inlet filters under dry and wet conditions were studied by Frydenlund et al. (1999). A total of 36 used filters absorbed a different amount of humidity. The particle filtration efficiency was nearly the same as for unused filters (comparing only filter class F7/EU7). The efficiency

5 of the filters was slightly decreased during the wet conditions compared with the dry conditions. The amount of contaminants in the filters was probably a result of the external conditions. Since thermotolerant molds were found in all filters, it is important to prevent leaks through filter components. Systematized method In order to systematize the method a flow chart has been developed to demonstrate the most efficient way of conducting those examinations. This iterative process is conducted for each step from I to V ( c.f. Figure 1) until MB conditions are satisfactory. Figure 2 Flow diagram, use of the method The process can either start from point 1 or 2 in Figure 2. The usually procedure is as follows; 1. Starting with a mapping of the technical hygienic condition, the process of revealing the risk of unwanted microbial growth. Good hygiene and good procedures for operation new revision in five years 2. If poor hygienic conditions or health problems need for MB examination. No unwanted microbiology operating procedures must be improved to reduce risk for future microbiological contamination. 3. If the MB examination is poor use the survey to identify the extent necessary for replacement and repairs of plant/equipment. Measures will be followed by MB control examination. MB examination is ok good procedures for operation and new review in five years 4. If MB controls/ examination is poor, necessary with further replacement and repairs of plant/equipment. Continue iterations of measures and MB examinations until MB is OK. This process should include necessary repairs until good hygiene is achieved. Always test microbiological state if poor microbiological conditions have been detected previously. RESULTS CASE STUDY B A four story building with basement, erected in 1961 in Trondheim, Norway. The ventilation units located on the roof supplied m3/h air to a gross area of m2. Coarse filters were replaced twice a year whilst particle filters, EU7/F7, were replaced once a year.

6 First one employee reported increasing health problems related to laboratories, later on several other employees with health problems in other areas were revealed. The basement experienced a severe water leakage three years before the complaints started, causing most of the flooring to be replaced (before 2005 and not included in figure 3). Firstly, the hygienic conditions seemed to be satisfactory. An inspection of the building and the ventilation plant concluded that the microbiological status for the indoor air ought to be verified. The monitoring results indicated that the ventilation system, which serves the entire building, was the source of the spread of mold spores including thermo tolerant species. The HygMic method was then used for a thorough survey. The results from this survey gave the basic information for concluding on : "Diagnosis" : mold growth and distribution of mold by the ventilation ducts Identification of "deviations" and possible causes: o Organic deposits on inlet grid o Dust and corrosion in ducting o Thermotolerant mold (fungi) in mineral wool from sound dampers o Limited accessibility to vital components Risk assessment/actions: o Basement floor pad replaced (before 2005) o Contaminated fresh air supply o Remove mineral wool in ventilation system o Remove floor felt/underlay in the technical room o Clean air supply units in each room Figure3Time-schedule for case study B (Jan 2005-Oct 2010).Measurements indicated by bars above time axis, while measures and information sessions indicated by bars underneath. In order to solve the problems a stepwise approach was chosen as described in figure 2. The whole process with appurtenant measures is described in Figure 3, see information regarding

7 measures underneath the x-axis. After each measure MB measurements were performed, thereby revealing the impact of the improvements. During this process, the active involvement of operation and maintenance personnel made this solution a success. Since the initial measures in 2006 the people responsible for the building operation have made most of the improvements. Based on the building owner's experiences from other projects, a total replacement of the whole ventilation system (including channels) would cost five times more than this project ( US$ instead of US$). Monetary cost includes a new ventilation unit, professional fees and measurements. A total renovation would also have included additional cost for temporary premises for the employees. DISCUSSION In buildings where indoor air complaints seem to be caused by the mechanical ventilation, the information resulting from a systematic hygiene mapping may be decisive for initiating MB sampling. If the first impression from a hygienic evaluation is negative, then a MB evaluation is needed. Even if the hygienic values at first seem to be satisfactory, a more systematic evaluation of the hygienic status might reveal risk like damaged silencers, materials that may have absorbed moisture, lack of drainage, etc. If MB measurements are needed, they should be carried out according to Figure 1 and 2. If the layout of the ventilation system differs from the one described in Figure 1, adjustments are necessary, for instance long distance between the air inlet and filter/heat exchanger and long or varying distance between filter/heat exchanger etc. and the occupants. To reveal hidden sources of MB contamination, the number of sampling locations needs to be increased. As a rule, MB sampling should be performed from air outlets close to the filter/fan and far away from the filter/fan. MB contamination of indoor air may be caused by other building-related damages. If sources happen to be located in the technical room, air borne spores may enter ducts through leakages. Mineral wool silencers will adsorb moisture creating a good environment for MB growth. If MB contamination is only found in the room air, it is very likely that the source is related to the building construction through leakages, flooding, moisture or condensation on cold surfaces. Unwanted MB found in occupant atmospheres should be examined thoroughly. If it is not detected in the supply air, then the construction should be examined. By applying the HygMic method, the impact of the ventilation system will be revealed. CONCLUSIONS A systematic approach is essential in order to reveal and solve reported health problems related to IAQ and MB contamination in an efficient way. Without applying a proven method, a lot of time and money will be wasted, in particular if large, complex ventilation plants are involved. A stepwise approach will speed up the process and uncover the most likely locations causing the problems. Thereby unnecessary health suffering, unsuccessful efforts and costs are prevented. This is of particular importance when ventilation plants are involved. The most important, however is that people suffering at their workplace will get a final answer and no longer need to be uncertain about being hypochondriacal or not. Bad hygienic conditions in and around ventilation ducting and other components are likely to cause microbial consequences.

8 In the studies performed so far, there has been found no biological contaminated systems with well-maintained and clean air intakes and ventilation ducts. A hygienic evaluation of the ventilation facilities may well be used for risk assessments of contaminated air intakes and ventilation systems. For a proper exposure risk evaluation, supplementary air sampling regarding microbiological contamination will be of importance. If no microbial problems are identified, future problems can be avoided by improving the hygienic status. This implies dedicated cleaning and maintenance activities. ACKNOWLEDGEMENT You may acknowledge the assistance provided by others to the work presented or in preparing this paper. Sources of financial support should also be noted. REFERENCES Ahlén, C., and Haugen, E.N HVAC-induced alterations in microbial flora of indoor air a potential for increased pathogenity of microbes? Proceedings of the 7th International Conference on Indoor Air Quality and Climate Indoor Air 96, Vol.3, 1996, pp Bluyssen, P., Seppänen, O., Fernandes, E., Clausen, G., Müller, B., Molina, J., and Roulet, C.A. 2001: AIRLESS A European project to optimize Indoor Air Quality and Energy consumption of HVAC-systems. In: Proceedings of CLIMA 2000, Naples. CEN European Standard. Draft pren Ventilation for non-residential buildings. Performance requirements for ventilation and room conditioning systems. Crandall, M., Sieber, W., and Malkin, R. HVAC and building environmental findings and health symptoms associations in 80 office buildings, Proceedings of IAQ 1996, pp Frydenlund, F., Haugen, E.N., Ahlén, C., Bryn, I. H., Davidsen, H., Hanssen, S.O., and Møgedal. G.T Macro- and micro evaluation of air intake a demonstration of the need for more optimal tools. Proceedings of the 9th International Conference on Indoor Air Quality and Climate Indoor Air 02 Vol.1, 2002, pp Frydenlund, F., Haugen, E.N., Kristiansen, O., Ahlén, C., and Hansen, S.O Study of used filters under dry and wet conditions. Proceedings of the 8th International Conference on Indoor Air Quality and Climate Indoor Air '99, Vol.4,1999, pp Lee, K.S., Bartlett, K.H., Brauer, M., Stephens, G.M, Black, W.A., and Teschke, K. 2004a. A field comparison of four samplers for enumerating fungal aerosols I. Sampling characteristics, Indoor Air, 14, Lee, K.S., Teschke, K., Brauer, M., and Bartlett, K.H. 2004b. A field comparison of four fungal aerosol sampling instruments: inter-sampler calibrations and caveats, Indoor Air, 14, Lysne, H.N., Ahlén, C., Stang, J., Kristiansen, O., Haugen, E.N., Frydenlund, F., and Hansen, S.O Hygienic conditions in ventilation systems and possible impact on indoor air microbial flora. Proceedings of the 8th International Conference on Indoor Air Quality and Climate Indoor Air 99, Vol.2,1999, pp Mendell, M.J., Lei-Gomez, Q., Mirer, A.G., Seppänen, O., and Brunner, G Risk factors in heating, ventilating, and air-conditioning systems for occupant symptoms in US office buildings, the US EPA BASE study, Indoor Air 2008; 18: Pasanen, A.L., Reponen, T., and Kalliokoski, P Seasonal variation of fungal spore levels in indoor and outdoor air in subarctic Climate. Proceedings of the 5th International Conference on Indoor Air Quality and Climate - Indoor Air '90, Vol. 2, 1990, pp Sieber, W. K., Stayner, L.T., Malkin, R., Petersen, M.R., Mendell, M.J., Wallingford, K.M., and Reed, L The National Institute for Occupational Safety and Health indoor environmental evaluation experience. Part Three: Associations between environmental factors and self-reported health conditions. Applied Occupational and Environmental Hygiene, 11(12), Struksnes, O. The effect of periodic change of air filters versus the working time of HVAC-plants. Diploma thesis, Rapp 03:51, NTNU Wargocki, P., Bako-Biro, Z., Clausen, G., and Fanger, P Air quality in simulated office environment as a result of reducing pollution sources and increasing ventilation. Energy and Buildings, 34,