###### Abstract  
Recently, tropospheric ozone has become a public health concern worldwide, along with the continuous battle against ambient fine particulate matter in countries like China. In this study, we investigate the impact of indoor ozone pollution using seven materials categorized as either wood-based panels or synthetic fibers, which were freely-stored in an office/lab environment. Most materials were considered as used and aged more than 1-2 years. An experimental apparatus was used to study ozone deposition and detect volatile organic compound (VOC) emissions from the specimens when exposed to ozone at three concentration levels: \(<\)10, 100, and 300 ppb. A simplified model is proposed to discuss ventilation requirements based on a standard room. We found that the mean ozone deposition velocities from the seven materials ranged from 0.005 to 0.062 cm-s\({}^{-1}\). Both the engineering wood and some of the synthetic fibers were, moreover, prone to ozone deposition. Second, 15 VOCs were found in the sampling air from a 24-VOC target list after ozone exposure. The emission rates of the VOCs from all seven materials were then determined. Third, when the ozone concentration in the outdoor air is not severely high, it is possible to use ventilation to maintain acceptable indoor air quality. e 2020 11 May 2020; 10 June 2020 10 June 2020 11 May 2020 11 May 2020 10 June 2020 11 May 2020 11 May 2020 11 June 2020 10 June 2020 10 June 2020 11 May 2020 11 June 2020 10 June 2020 1  
In the indoor environment, ozone concentrations vary as a function of both the outdoor contributions and indoor conditions [11; 12; 13] and are generally lower than the outdoor concentrations [14]. Early studies indicate that the ratios of indoor to outdoor ozone concentrations are mainly in the range of 0.2-0.7 [12]. However, indoor exposure can constitute up to 60% of a person's total exposure to ozone [15; 16]. Copiers, laser printers, electronic air cleaners, and ozone generators can act as ozone sources, with emission rates ranging from 0.1 to 100 mg\(\cdot\)h\({}^{-1}\), which are comparable to outdoor air as a source of ozone on a highly polluted day [11]. In the absence of indoor sources, the indoor ozone concentration depends on the outdoor ozone concentration, air change rate (ACH or ventilation rate), and removal rate of indoor surfaces, including human hair, skin and clothes, and ozone-initiated reactions with organic gases [17; 18; 19; 20]. Among the various mechanisms, surface removal and ventilation play major roles in changing indoor ozone concentrations because the gas-phase reactions initiated by ozone are slow for most VOCs compared to ACH and the surface removal rate under typical indoor conditions [12; 17; 21; 22]. The effects of surface removal and ventilation on indoor ozone concentrations are coupled for the following reasons. On the one hand, although surface removal is a prevalent and effective way to eliminate indoor ozone, it is sometimes accompanied by harmful or irritating byproducts, including C1-C13 carbonyls, dicarbonyls, hydroxycarbonyls, and ultrafine particles [23; 24; 25], which may require higher ventilation rates to dilute [26]. On the other hand, it is obvious that outdoor ozone can be brought indoors by ventilation. Therefore, the indoor air concentrations of ozone and its byproducts may not be improved by increasing the ventilation rate. One possible solution is to adopt mass accretion on material surfaces, which may passively remove indoor ozone while producing no byproducts or only benign byproducts [27; 28; 29]. At present, this potential improvement measure has not attracted enough attention in China. Throughout the available literature, the relationships between ozone and indoor materials has been extensively studied, mostly focusing on carefully-controlled, newly-obtained materials in developed countries. However, very few studies were conducted under Chinese scenarios using aged materials on a large scale [17].