DETERMINATION OF ODOR DETECTION THRESHOLD FOR THE MIXTURES OF n-butanol, INDOOR AIR AND OZONE

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1 Proceedings of ECOpole Vol. 2, No Mariusz SKWARCZYŃSKI 1, Bernard POŁEDNIK 1 Marzenna DUDZIŃSKA 1 and Paweł NIEWĘGŁOWSKI 1 DETERMINATION OF ODOR DETECTION THRESHOLD FOR THE MIXTURES OF n-butanol, INDOOR AIR AND OZONE OZNACZANIE STĘśEŃ PROGOWEJ WYCZUWALNOŚCI WĘCHOWEJ DLA MIESZANIN POWIETRZA WEWNĘTRZNEGO, n-butanolu I OZONU Summary: There are two approaches to the use of ozone in occupied spaces. The first one is that ozone has little ability to effectively deodorize indoor air and its use could have harmful health consequences. The second approach indicates that ozone in small concentrations can eliminate indoor air contaminants including odor pollutants. The paper presents the results of determination of the odor detection threshold concentrations C th of n-butanol in mixtures with indoor air deodorized by ozone. The initial concentrations of n-butanol ranged from to mg/m 3. The doses of ozone that were used were lower than the ones permissible by standards and ranged from to ppm. The olfactometric method with sample dynamic dilution was applied during sensory assessments of the samples. The results discussed in the paper confirmed ozone s deodorizing effects on the perception of n-butanol present in the indoor air. Assuming that ozone could be similarly effective in reducing other indoor air odor pollutants and that there is a lack of harmful by-products, small doses of ozone could be considered as a reducer of the indoor air odor onerousness. Keywords: sensory evaluations, odor pollutants, odor detection threshold, n-butanol, ozone, indoor air quality A lot of data concerning the use of ozone for odor deodorization indoors can be found in the literature [1-6]. The majority of this data does not present scientifically substantiated conclusions concerning the safety and effectiveness of ozone in controlling indoor air odor pollutants. Many researchers and health professionals have refuted claims that ozone may be used in occupied spaces [6, 7]. They consider ozone to have potentially harmful health consequences. According to them these health consequences may be even more harmful over long-term exposure or when ozone doses are higher. Some researchers believe that ozone has little ability to eliminate indoor air contaminants when it is used in concentrations not exceeding the public health standards [7, 8]. They also neglect the fact that ozone is able to render any chemical contaminant harmless. Such statement is based on scientific research which shows that the reactions of ozone with the majority of indoor air pollutants are very slow and they cannot be practically taken into consideration [6, 7, 9]. Furthermore, ozone could create various harmful and irritating by-products with pollutants which enter into reactions quite fast. On the other hand, there is a lot of research which indicates that ozone can effectively eliminate indoor air contaminants including odor pollutants. The adherents of this theory claim eg that the use of ozone generators which allow for ozone concentration control in the indoor air and maintaining it below the health standards is an acceptable way of improving indoor air quality. 1 Faculty of Environmental Engineering, Lublin University of Technology, Nadbystrzycka 40B, Lublin, tel , m.skwarczynski@pollub.pl

2 108 Mariusz Skwarczyński, Bernard Połednik, Marzenna Dudzińska and Paweł Niewęgłowski Materials and methods The odor detection threshold concentrations C th of n-butanol in defined mixtures with ozone in the indoor air were determined by means of a dynamic method using a modified Ecoma T07 olfactometer [10]. Chromatographic analysis (GC/MS) of the mixtures were also performed. The sensory analysis and sample preparations were carried out in an air quality laboratory at the Faculty of Environmental Engineering at the Lublin University of Technology (LUT). a) b) Fig. 1. Scheme of olfactometric laboratory and sample preparation procedure The scheme of the olfactometric laboratory is shown in Figure 1a. Figure 1b presents the procedure of sample preparations. The olfactometer with diffuser tubes for sensory assessments together with the assessors seats were located inside the environmental chamber. The dosimetric and control part of the olfactometer were beyond the assessors view. The indoor air mixtures of n-butanol deodorized by chosen doses of ozone were dynamically diluted with conditioned odorless air in the olfactometer and evaluated by the sensory panel [11, 12]. The initial concentrations of n-butanol in indoor air mixtures ranged

3 Determination of odor detection threshold for the mixtures of n-butanol, indoor air and ozone 109 from to mg/m 3. Ozone of 20% concentration was obtained in a corona discharge generator. A photometric ozone analyzer (Anseros 6030) was used to monitor the ozone concentration. The used doses of ozone were lower than the ones permissible by standards [6, 8] and ranged from to ppm. The results of the sensory assessments performed according to the European Standards [12], were registered by the computer. The sensory panel was recruited from the LUT students. Male and female, non-smoking panelists were aged from 20 to 23. Results and discussion The concentration of n-butanol in the investigated samples decreases with the increase of the ozone dose, due to decomposition processes, what was confirmed by chromatographic measurements. This has implications in the required lower dilutions of the samples for odor to be detected which, in turn, means the increase of the odor detection threshold concentrations C th. The relation between C th and ozone dose is shown in Figure 2. It can be seen that the C th increases with the increase of the ozone dose. This gives evidence of the fact that with the same initial n-butanol concentration in the sample, the greater dose of ozone, the greater concentration of n-butanol (lower dilution of the sample) is needed to be perceived. Fig. 2. Odor detection threshold concentration vs dose of ozone The perception deodorization efficiency, which relies on ozone neutralization and masking processes of n-butanol odor was determined on the basis of the performed sensory assessments. The following equation was derived: η p = (C th, o C th )/ C th, o where: C th - the odor threshold concentration for n-butanol, C th, o - the odor threshold concentration for n-butanol deodorized by ozone.

4 110 Mariusz Skwarczyński, Bernard Połednik, Marzenna Dudzińska and Paweł Niewęgłowski Chromatographic measurements of n-butanol concentrations were utilized to determine the chemical deodorization efficiency. This efficiency is due to ozone chemical reactions which lead to the decomposition of n-butanol. The efficiency was calculated from the formulae: η c = (C o C ) / C o where: C - the concentration of n-butanol in the sample, - the concentration of n-butanol in the sample decomposed by ozone. C o The changes of both efficiencies with the increasing doses of ozone are shown in Figure 3. Fig. 3. Relationship between deodorization efficiency and dose of ozone It is seen that chemical deodorization efficiency (curve a) outnumbered the perceived deodorization efficiency (curve b) and the differences rise with the increased doses of ozone. Such relations could prove that, in given conditions, when higher doses of ozone are applied, the remaining ozone, which does not enter into a reaction with n-butanol influences the odor perception. There is a range of ozone doses, which when exceeded, does not significantly increase the deodorization efficiency. In practice it means that the use of ozone doses below this range is advantageous for indoor air quality improvement. Additionally, it is desirable to apply decomposing filters for ozone, which does not take part in the deodorization processes. Conclusions On the basis of these initial results of the performed sensory assessments and chromatographic analysis for deodorized mixtures of n-butanol and indoor air ozone could be considered as a reducer of odor onerousness. It could also be treated as an agent which improves indoor air perceived quality. However, further research is necessary to

5 Determination of odor detection threshold for the mixtures of n-butanol, indoor air and ozone 111 disentangle the problem of potential harmful by-products and to determine under what circumstances ozone improves indoor air quality with benefits to the indoor space users. References [1] EPA 402-K U.S. EPA, [2] Kilham L.B. and Dodd R.M.: The Application of Ozone for Air Treatment. Proc. 14 Ozone World Congress, Dearborn, MI 1999, Vol [3] Kim-Yang K., Daves S.H., Hill D.J. and Bernurth R.D.: Soc. Eng. Agric. Food Biol. Systems, 2002, [4] Kośmider J. and Wyszyński B.: InŜ. Chem. Proc., 2001, 22, [5] Tatoj P.: InŜ. Aparat. Chem., 2002, 1, [6] U.S. Environmental Protection Agency EPA-600/R , [7] Palica M., Chmiel K., Kaczyńska T. and Tatoj P.: Chem. InŜ. Ekol. 1999, 6(4), [8] Rozporządzenie ministra pracy i polityki społecznej z dnia 29 listopada 2002 (DzU Nr 217, poz. 1833). [9] Wainman T., Zhang J., Weschler C. J. and Lioy P. J.: Environ. Health Perspect., 2000, 108(12), [10] Olfaktometr TO7 - System Mannebeck Operating Manual, [11] Borkowska I.: PhD. thesis. Wydział InŜynierii Środowiska, Politechnika Wrocławska, Wrocław [12] PN-EN 13725, OZNACZANIE STĘśEŃ PROGOWEJ WYCZUWALNOŚCI WĘCHOWEJ DLA MIESZANIN POWIETRZA WEWNĘTRZNEGO, n-butanolu I OZONU Streszczenie: Rozpatrywane są dwa podejścia przy stosowaniu ozonu w pomieszczeniach, w których przebywają ludzie. Według pierwszego, ozon ma małą zdolność do skutecznej dezodoryzacji powietrza wewnętrznego oraz moŝe mieć szkodliwe działanie na zdrowie człowieka. Według drugiego, ozon stosowany w małych stęŝeniach moŝe eliminować zanieczyszczenia w powietrzu, włącznie z zanieczyszczeniami zapachowymi. W pracy przedstawiono wyniki określania stęŝeń progowej wyczuwalności węchowej S pw dla mieszanin n-butanolu z powietrzem wewnętrznym z dodatkiem neutralizującego zapach ozonu. StęŜenia n-butanolu mieściły się w zakresie od 0,079 do 25,312 mg/m 3. Stosowane dawki ozonu były wielokrotnie niŝsze od dopuszczalnych i zmieniano je w przedziale od 0,004 do 0,042 ppm. Przy pomiarach sensorycznych wykorzystano olfaktometryczną metodę rozcieńczeń dynamicznych. Przedstawione w pracy wyniki potwierdziły neutralizujące działanie ozonu na zapachową percepcję n-butanolu obecnego w powietrzu wewnętrznym. Przy załoŝeniu podobnej skuteczności redukcji innych zapachowych zanieczyszczeń i przy braku szkodliwych produktów pośrednich małe dawki ozonu moŝna byłoby rozpatrywać jako czynnik zmniejszający uciąŝliwość zapachową powietrza wewnętrznego. Słowa kluczowe: sensoryczne pomiary, zanieczyszczenia zapachowe, stęŝenie progowej wyczuwalności węchowej, n-butanol, ozon, jakość powietrza wewnętrznego