PASSIVE METHODS FOR MONITORING INDOOR AIR QUALITY IN MUSEUMS

Transcription

1 PASSIVE METHODS FOR MONITORING INDOOR AIR QUALITY IN MUSEUMS T Iwata 1, C Sano 2, M Hori 3, H Tsukahara 4 and N Oba 4 1 Department of Architecture, Tokai University, Japan 2 Conservation Science Dept., Tokyo National Research Institute of Cultural Properties, Japan 3 Graduate school of Environment and Information Yokohama National University, Japan 4 Graduate student, Graduate School of Engineering, Tokai University, Japan ABSTRACT The purpose of this study is to develop a small passive sampling kit which can be suitable as a way of measuring IAQ in museums. Test measurements were conducted in a 20-year old museum. As well as temperature and humidity, the concentrations of ammonia, formaldehyde, nitrogen dioxide, acetic and formic acids, TVOC, ozone, salt and acidity/alkalinity were also measured by a trial sampling kit. The concentrations of nitrogen dioxide in the display cases were lower than that in the rooms, while the concentrations of formaldehyde in the display cases were higher. The results of the ph paper showed non-uniform discoloration and implied that both alkaline and acidic pollutants existed. Since the concentration of ammonia was very low, it was expected that the other alkali also existed. The validity of the small sampling kit was shown to measure IAQ in museums without preventing visitors from appreciating art. INDEX TERMS Museum, Passive sampling, Acidity/Alkalinity, Nitrogen dioxide and Formaldehyde INTRODUCTION Our previous papers (Hori, Nakamura, Tsukahara, et al. 2000), (Hori, Iwata, Tsukahara, et al. 2001) investigated indoor air quality in both a newly-built museum and a 10-year-old museum. Each used both active and passive sampling methods. It was found that the passive sampling method was more suitable for museums. However, museum s air quality includes many kinds of pollutants, so it is necessary to reduce the number of measured pollutants for efficiency of analysis. Conditions, such as the building materials, the kinds of cultural collections and surrounding environment, should be identified before measurement, as they determine the compulsory pollutants measured. The purpose of this study is to develop small sampling kit of passive samplers. In this study, the validity of the passive sampling kit which was more compact than the previous study s samplers was examined. Samples were taken in both exhibition rooms and display cases to determine the difference between the two. METHODS Test measurements were carried out in a museum, located near the ocean in Shizuoka prefecture in February, Table 1 shows the outline of the museum. The measurement was conducted in five exhibition rooms, five display cases in each exhibition room, a storage room, the lobby and outside. The HVAC systems were operated from 9:00 to 17:00. Commonly display cases were required to have an airtight seal, but the display cases in this museum had small openings in widths of 7cm. Inside the display cases were lights. Therefore, * Contact author iwata@keyaki.cc.u-tokai.ac.jp 178

2 it is assumed that the display cases have airflow caused by convection, so passive sampling could be used. Figure 1 shows the sampling kit used in this study. Table 2 shows the methods of sampling and analysis. All measurements were passive sampling methods, except salt, TVOC, suspended fungal spores and SPM. Twenty-four hours of exposure were required for the measurements of salt, TVOC and acidity/alkalinity and one week of exposure for the measurements of ammonia, nitrogen dioxide, acetic and formic acids, ozone and formaldehyde. Suspended fungal spores and SPM were collected for 2 minutes. The ph paper used is developed by Tokyo National Research Institute of Cultural Properties. Water vapor saturated with pollutants in the air is caught on the ph paper. The change in color of the paper shows the inclination toward acid/alkali. As the ph paper changes from acidity to alkalinity the paper s color goes from yellow to blue. It is important to allow enough time to lapse to accurately read the final color results (Sano. 1999). Table 1. Outline of the museum. Date of starting construction work November, 1977 Date of furnishing December, 1981 Date of opening February, 1982 Structure SRC Total area (Total exhibition rooms area) 13898m 2 (1992m 2 ) Materials of the interior surface Storage rooms Floor, Ceiling, Wall ; Spruce Exhibition rooms Floor; Japanese oak Ceiling, Wall; Cloth, Paint Surroundings 1km from ocean, light traffic Figure 1. Sampling kit in this study. Table 2. Method of sampling and analysis. Object Sampling methods Analysis Ammonia 10% phosphoric acid Spectro photometer Nitrogen dioxide Filter badge (ADVANTEC) Spectro photometer Acetic acid, Formic acid Formaldehyde Ozone 1 TVOC 2 10%TEA Filter badge, 2%glycerin adhering to silica gel passive tube 10%TEA aq.in vial DNPH aq.in vial Sodium nitrite filter paper Activated carbon tube (flux 300ml/min) Ion chromatography 10%TEA:Spectro photometer DNPH: Liquid chromatography Ion chromatography Gas chromatography Suspended fungal spores Centrifugal sampler RCS Cultivated by 24C in 6 days Salt 2 Teflon filter (flux 300ml/min) Gas chromatography Acidity/Alkalinity Discoloration the ph paper SPM Laser distributed particulate matter meter LD-1 (SHIBATA) Temperature, Humidity Portable logger (Espec) 1: measurement was conducted in outside and 1 exhibition room 2: measurement was conducted in an exhibition room 179

3 RESULTS AND DISCUSSION Difference in the concentration between display case and exhibition room. Nitrogen dioxide. Figure 2 shows the concentration in the exhibition rooms and the display cases. The outdoor concentration was lower than that in our previous measurements conducted in urban areas (Hori, Nakamura, Tsukahara, et al. 2000). However, indoor concentrations were generally higher. The concentrations of nitrogen dioxide in Exhibition rooms 1 and 4 were higher than the recommended value by Thomson, 5 ppb (Thomson. 1978). The concentrations in the display cases which had small openings were lower than that in the exhibition rooms. The concentration of nitrogen dioxide in the display cases could be reduced by the absorption of nitrogen dioxide because the absorption surface in the display case was large for its volume. Formaldehyde. Figure 3 shows the concentration in the exhibition rooms and the display cases. The concentrations of formaldehyde in all spaces were lower than the recommended value, 80ppb (Maroni, Seifert and Lindvall. 1995). Comparing with the DNPH passive method and the TEA passive method, the concentrations by the DNPH methods were higher than the TEA methods. Comparing with the exhibition rooms and the display cases, both of TEA method and DNPH method showed that the concentrations in the exhibition rooms were lower than that in the display cases. This result was the opposite of the nitrogen dioxide result. Because the nitrogen dioxide came from outdoors, the concentrations in the exhibition rooms were higher than the display cases. On the other hand, because the formaldehyde was emitted from inside, perhaps emitted from display case materials, the concentrations in the display cases were higher than the exhibition rooms. From this result, the display cases could have little ventilation although they had small openings and they might have formaldehyde emissions. It is required that low emittance of formaldehyde from the materials of a display case has been confirmed. Concentration in display case Room number Concentration in exhibition room Figure 2. Concentration of NO Concentration in display case DNPH method TEA method Room number Concentration in exhibition room Figure 3. Concentration of formaldehyde. Acidity/Alkalinity ph paper. Figure 4 shows the results of the ph paper. Non-uniform discoloration implies that both alkali and acid pollutants exist. The ph paper was discolored from outside to inside. First, the acid changed color into yellow and then from the perimeter alkali changed the color again. This phenomenon was caused by the difference in the saturation rate between alkali and acid. Therefore, Exhibition rooms 1, 4 and 5 and all display cases included both alkali and acid. The outside and the storage room showed acidity. Exhibition rooms 2 and 3 and the 180

4 lobby where the neutrality is seemingly indicated are marked? in Figure 4, because they also have the possibility that both alkali and acid exist. Alkali + +? +? ? Acid + E1 +? +? ? + D1 E2 D2 E3 D3 E4 D4 E5 D5 S L O Neutral E: Exhibition room D: Display case S: Storage room L: Lobby O: Outdoor Acidic Figure 4. Results of the ph paper. Acidity. Nitrogen dioxide is one of the suspected acid pollutants. The concentrations of nitrogen dioxide in the lobby, the storage room and outdoors were 6.8 ppb, 5.4 ppb and 7.9 ppb while the concentrations of the exhibition rooms and the display cases ranged from 0.5 to 5.6 ppb as shown in Figure 2. The acidity of the outdoor air should be caused by nitrogen dioxide although the concentration was lower than that in urban areas. In the lobby where the neutrality was seemingly indicated in Figure 4, the coexistence of alkali was suggested by nitrogen dioxide concentration. Similarly, from the concentrations of nitrogen dioxide in Exhibition rooms 2 and 3 as shown in Figure 2, it was assumed that both rooms included alkali. The difference between uniform and non-uniform discoloration is explained by the difference in the absorption rate on the ph paper which is affected by air humidity. The other suspected acid pollutants were acetic and formic acids. Table 3 shows the amount of acetic and formic acids. The acidity of the storage room should be caused by acetic and formic acids as well as by nitrogen dioxide. Also, in Display cases 1 and 5, the amounts of acetic acid which is harmful for lead (Tetreault, Sirois and Stamatopoulou. 1998) are high. Careful observation is necessary, according to kinds of cultural collections or artworks in these cases. The sampling coefficients of the passive samplers for acetic and formic acids have been calculated. Table 3. The amount of the acetic and formic acids. Measurement area Acetic acid (µg) Formic acid (µg) Storage room Exhibition room Display case Display case Alkalinity. The concentrations of ammonia in all spaces were lower than 1ppb. This museum was 20 years old. Therefore the concentration of ammonia showed low, stable values. However, the ph paper in the exhibition rooms, the display cases and the lobby identified the existence of alkali pollutants. Therefore the other alkaline pollutants, such as amine, possibly existed. VOCs Figure 5 shows concentrations of VOCs in Exhibition room 5 compared to the newly-built museum (Iwata, Hori and Tsukahara. 2001). The broken lines show WHO guidelines 181

5 presented by the European office for human health (Maroni, Seifert and Lindvall. 1995) and the number in the parenthesis were the recommended value in µg/m 3. The concentration of TVOC was 123µg/m 3. The concentration of aromatic hydrocarbons and ketones in this museum were lower than the newly-built museum (Hori, Nakamura, Tsukahara, et al. 2000). However, the concentration of halocarbons in this museum was 33 µg/m 2 which was higher than that in the newly-built museum and the recommended value. As halocarbons, p-dichlorobenzene which was used in insecticides and mothballs, showed high values. It is calculated that the concentrations of VOCs in the display cases would be higher than that in their rooms, and as such, the case materials must be carefully selected. However the effect of each VOC on art works has not been clarified. Others The air temperature in the exhibition rooms, the display cases and the storage room were kept at C, C and 21.0C. The relative humidity in the exhibition rooms, the display cases and the storage room were kept at %, % and 55.9%. The outdoor concentration of ozone was 8 ppb and the concentration of ozone in exhibition room 2 was 2 ppb. Thomson s recommendation, less than 1 ppb (Thomson. 1978), was difficult to measure precisely by the passive sampler. Figure 6 shows the concentrations of SPM and airborne culturable fungi. For SPM the number in the parenthesis shows the number of the samples and the upward and downward bars show the maximum and minimum values respectively. The concentration of SPM was lower than the guidelines (0.15mg/m 3 ) which was presented in Law for Maintenance of Sanitation in Buildings to keep workers health. At 100cm from the floor, no difference in the concentration of SPM can be found between rooms. However when the measured height was 15cm, the concentration of SPM was different between the rooms. It is considered that the low measured height can be easily affected by visitor s movements. Recommended value Alkanes (100) (Unit: µg/m 2 ) Sum of TVOC (300) Other (50) Ketones (20) 0 Esters (20) Aromatic hydrocarbons(50) Terpenes (30) Halocarbons (30) : Results in this study : Results in the newly-built museum (Hori et al.2000) Figure 5. Concentrations of VOCs. SPM (mg/m 3 ) Outdoor SPM E.R.1 E.R.2 (5) E.R.3 Room Fungi (5) (5) (5) (4) (3) (4) E.R.4 E.R.5 Lobby E.R: Exhibition room Figure 6. SPM and airborne culturable fungi Airborne fungi (CFU/10L) The concentration of airborne culturable fungi was less than 35 CFU/m 3. It is approximately 10% of the concentration in houses (Shinohara, Iwata and Tsukahara. 2001). However, it cannot be said that these fungi concentrations are sufficiently low as museum environment, because measurements by RCS sampler under low concentration include unreliability and no guidelines for airborne fungi in museums have been presented. 182

6 The concentration of salt in exhibition room 5 was 1.5µg/m 3 and that in display case 4 cannot be detected. This museum was located near the ocean but it was not affected by air flow from the ocean because of the different altitude. CONCLUSION AND IMPLICATIONS From these test measurements by the sampling kit in the museum, the following conclusions were obtained; The concentrations of nitrogen dioxide in the display cases were lower than the exhibition room, while the concentrations of HCHO in the display cases were higher. These results were caused by differing the sources, namely one being indoor and the other outside. The results of the ph paper should be interpreted carefully, especially when non-uniform discoloration is shown. Both alkali pollutants and acid pollutants existed. Because the concentration of ammonia which was detected was quite low, the ph paper in the exhibition rooms, the display cases and the lobby, showed the existence of the alkali pollutants and the acid pollutants. In the concentrations of VOCs in the exhibition room, the concentration of halocarbons, which include p-dichlorobenzene used in insecticides and mothballs was high. Further studies are necessary to develop a simpler and smaller sampling kit for the cultural facility managers/custodians. ACKNOWLEDGEMENTS This study has been carried out thanks to the help of Nihon Air Filter, Co. and the museum. REFFERENCE Hori M, Iwata T, Tsukahara H, et al Development of simple methods for monitoring indoor air quality in museums. Proceedings of Clima 2000 Iwata T, Hori M and Tsukahara H Field investigation on IAQ in museums and examination of methods for monitoring, Pilot study for air quality guidelines in museums, Part 1. Journal of Architecture, Planning and Environmental Engineering (Transactions of AIJ), No.550 pp Maroni M, Seifert B and Lindvall T Air quality monographs vol3. Indoor air quality, A comprehensive reference book, Elsecier Hori M, Nakamura Y. Tsukahara H. et al Field investigation of indoor air quality in a museum. Proceedings of Healthy Buildings Vol. 4, pp Sano C Air Pollutants Trapped in a ph Test Paper for Indoor Air/Hensyoku Shikenshi. Hozon Kagaku, No38 pp Shinohara F, Iwata T and Tsukahara H Field investigation on fungi and mites in houses Summaries of Technical papers of Annual meeting Architectural Institute of Japan, Environmental Engineering 2, pp Tetreault J, Sirois J and Stamatopoulou E Studies of lead corrosion in acetic acid environment. Studies in Conservation. Vol. 43, pp Thomson G The Museum Environment. Bufferworth Heinemann 183