Universitet Evaluation of building materials individually and in combination using odour threshold

This paper presents results of an experimental procedure to observe the impact of building materials on perceived air quality. An untrained panel of 25 adult subjects perceived the quality of polluted air in smallscale chamber settings. The air pollution was generated by emissions from individual materials, by combinations of these materials and by mixtures of emissions from single materials. The results showed that the exposure response relationship varies for one of the tested materials compared with the others. The study also confirmed that interaction among building materials is often negligible from the perception point of view, which is in contradiction with the findings published in the literature. Further analysis of data indicated that linear addition of olfs of single materials is still a permissible simplified method to estimate the sensory pollution load in the presence of combinations of building materials in the absence of any other practical technique. Introduction More than several hundred different compounds have been identified in indoor air. Many are emitted from indoor building materials, construction products and other indoor pollution sources. Some are also present in outdoor air. The presence of these polluting compounds may make the environment unpleasant for occupants, and cause health risks and symptoms, referred to as the Sick Building Syndrome [1,2]. Therefore, it is important to keep the concentration of air pollution in indoor environments at the lowest possible level. The state-of-the-practice to adjust required ventilation rate for acceptable indoor air quality (IAQ) is to follow the ASHRAE Ventilation Standard 62-2004 [3], which requires that the ventilation rate specification is based on the contribution from occupants as well as the building materials and equipment. Moreover, the ASHRAE Standard 62-2004 specifies that higher air ventilation rates are required when the emissions from indoor sources increase, which would result in higher energy consumption and increased risk of local thermal discomfort due to draft, as well as increase in greenhouse gases. Controlling the sources of emissions by avoiding high polluting building materials, and so reduce emissions and Professor Fariborz Haghighat Concordia University, Department of Building, Civil and Environmental Engineering, 1455 de Maisonneuve Blvd. W., Montreal, Quebec, H3G 1M8, Canada Tel. (514) 848-2424 ext. 3192, Fax (514) 848-7965, E-Mail [email protected] © 2006 SAGE Publications DOI: 10.1177/1420326X06072735 Accessible online at http://ibe.sagepub.com Original Paper Indoor Built Environ 2006;15;6:583–593 Accepted: August 8, 2006 Evaluation of Building Materials Individually and in Combination Using Odour Threshold Behnoush Yeganeh Fariborz Haghighat Lars Gunnarsen Alireza Afshari Henrik Knudsen Concordia University, Department of Building, Civil and Environmental Engineering, Canada Energy and Indoor Climate Division, Danish Building Research Institute, Horsholm, Denmark at Aalborg University Library on December 15, 2009 http://ibe.sagepub.com Downloaded from minimise ventilation requirements, seems to be a more appropriate strategy to improve IAQ. This requires knowledge of the pollution sources and prediction of the impact of different materials on the perceived air quality during the design of a new building, or the renovation of an existing one. Fanger [4] proposed a method to quantify the acceptability of indoor air and identify the causes of building occupants’ complaints when exposed to different building materials. He introduced the concept of perceived air quality and source strength by defining the units decipol and olf. Olf is a unit which quantifies the source strength of air pollution, while decipol is a unit which describes the perceived air quality [4]. Based on this concept, the perceived air pollution from any source is defined as the concentration of human bioeffluent or number of standard persons that would cause the same level of dissatisfaction as the actual pollution source. Fanger [4] also suggested that individual olf values of two sources emitting pollutants of the same nature can be added to predict the source strength of their combination. However, other studies have shown that the exposure response to different concentrations of air pollutants differ from one material to another and from the response to the human bioeffluent [5–8]. The discrepancy in the results obtained from different experiments leaves this area of research vague in offering a defined and predictable response for different building materials, which may need to be further investigated before any generalisation is possible. On a further step to investigate the possibility of predicting the source strength of a combination of materials, an inconsistency in findings can be noticed. According to one approach, predicting the source strength of a combination of materials can be based on the linear addition of pollution loads generated by individual indoor sources [9–10]. However, further study showed that this simplification may not be an accurate approximation in determining air quality and the required ventilation rate, as it overestimates the actual values for combinations of materials when the addition of source strengths of individual materials is compared with the source strength of the combination of materials [6]. However, due to the limited number of studies, it is difficult to make a strong conclusion regarding the overestimation of the linear addition of individual source strengths versus the actual values. Moreover, the results are limited to the number and type of materials used, the specific test conditions, and the techniques used in interpreting data. Interactions between building materials, causing the emissions generated by one material to be adsorbed on the surface of another, has previously been proven by using a numerical method, as well as analytical and sensory measurements [7,11,12]. However, this phenomenon and its effect on sensory assessment have not been studied in depth. In other words, no study has been conducted to show whether the interactions between different building materials will actually affect the perception. The shortcomings of previous investigations that observed the effect of sorption on perceived air quality leaves this phenomenon as a promising area of research. This study aimed to evaluate the quality of perceived air when pollution was generated by three different building materials, and to examine the possibility of generalising the exposure response relationships of the three investigated building materials to the one from human bioeffluents. Furthermore, the addition theory of sensory pollution loads for different single materials to predict the level of acceptability in the presence of a combination of materials was validated for the examined building materials. Most importantly, the existence of any sensory interaction between building materials that influence the perception from a combination of materials as the responsible cause was further investigated. Materials and Methods Set-up Figure 1 depicts the three types of set-ups considered to fulfil the aim of the present study. In the first set-up, called the single set-up, a sensory panel assessed the quality of air polluted by emissions from three individual building materials. This set-up (Figure 1(a)) considered the sensory impact of a single material at a time. Each material was placed individually in a single test chamber of CLIMPAQ type [13], with the inlet airflow being set to 0.9L·s . In the second set-up, the combination set-up, the concurrent effect of two or three materials was studied to evaluate if adsorption of pollution from one material onto another material would have an impact on the accuracy of the simple olf-based addition theory for pollution loads. For this purpose, materials were placed simultaneously inside one CLIMPAQ. The inlet airflow rate to test chambers in this set-up was also adjusted to 0.9L·s . Figure 1(b) shows the combination set-up for two materials. In the third set-up, the mixing set-up, sensory subjects assessed the quality of air when polluted by mixtures of emissions from two or three materials. In this set-up 584 Indoor Built Environ 2006;15:583–593 Yeganeh et al. at Aalborg University Library on December 15, 2009 http://ibe.sagepub.com Downloaded from (Figure 1(c)), two or three single materials were placed separately in different individual test chambers to eliminate the effect of interaction among them. The exhausts from these chambers were mixed in a separate chamber before being assessed by panel members. Inlet airflow to the test chamber was adjusted to 0.45L·s 1 in the case of two building materials, and 0.3L·s 1 in the case of three building materials. The airflow rate adjustments, along with the adjustments in the samples’ areas (which will be described in detail in following sections), were made to keep a constant area-specific airflow rate (Q/A) inside test chambers for every set-up throughout the experimental procedures. An empty single chamber assessment was also performed to provide the level of acceptability in the absence of building materials (background level). Chamber Description Twenty-one CLIMPAQ type test chambers were used for this experimental study. The inlet air to the CLIMPAQs and test room were provided by an air conditioning system being supplied with outdoor air. The supply air to the air conditioning system was filtered using a class EU7 fine filter, a charcoal filter and an additional class EU7 fine filter, in series. The exhaust air from each CLIMPAQ was led to a cone for sensory assessment. The mean value of airflow rate through the cones was 0.87L·s 1 with a standard deviation of 0.04, which was close to the recommended airflow rate for sensory studies [13]. The area-specific airflow rate (Q/A) in the CLIMPAQs was identical to the one of a model room with dimensions of 3.2 2.2 2.4m (length, width and height, respectively) and an air change rate of 2h 1 as defined by the Nordtest Method [13]. An air dilution system was installed on all set-ups in order to attain different concentrations of pollutants for sensory assessment [8]. Four sets of orifice plates were used to achieve 1, 1/2.5, 1/10 and 1/20 of the concentration of the pollutants in test chambers. In the mixing set-up, this system was installed solely on the mixing chamber. Figure 2 shows the test chamber with an installed dilution system used for the experimental procedure. Building Products and Sample Preparation Painted gypsum board, carpet with a textile backing and linoleum were selected as the materials used in this study, representing major groups of building products often used indoors. All the building products were new and came in sealed packages to minimise the loss of odour before the initiation of experimental work. Samples of materials were prepared immediately upon purchasing and they were cut to the required size (Table 1) based on the model room defined by the Nordtest Method [13]. Samples were preconditioned for 4 weeks at an air temperature of 21.9±1.8°C and a relative humidity of 56.7%±5.6% by hanging in a large wellventilated room. After 4 weeks of preconditioning, and before being put inside CLIMPAQs, samples of each of the flooring materials were stapled together, back to back, to reduce emissions from their back sides. Samples of building 585 Indoor Built Environ 2006;15:583–593 Odour Threshold of Building Materials Fresh air For assessment