## 2 Materials and Methods
### Environmental Chamber Set-Up  
Both the ozone deposition velocities and VOC emissions were measured in a laboratory chamber apparatus, as shown in Figure 1. A schematic of the apparatus is shown in Figure 2, including two 50 L stainless-steel emission chambers (No. 1 and No. 2; the inner dimensions for each chamber were 40 cm \(\times\) 39 cm \(\times\) 31.7 cm).  
Each of the 50 L chambers was equipped with 18 on/off ports, nine on each side, as shown in Figure 1b, as air inlets or outlets for exhaust, sampling, etc., and the leakage rate of each chamber was measured at 5-10%. All the tubes were made of polytetrafluoroethylene (PTFE). Before each round of testing, the inner surfaces of the emission chambers were scavenged orderly by medicinal alcohol, deionized water, heating, and clean air to minimize the sink and source effects. Chamber No. 1 was dedicated to investigating the effects of ozone, e.g., the deposition velocities and the primary and secondary VOC emissions, at either 100 ppb (i.e., a fairly-polluted level, approximately 214.3 \(\upmu\)g-m\({}^{-3}\) under standard conditions) or 300 ppb (i.e., an extremely-polluted scenario, equivalent to 642.9 \(\upmu\)g-m\({}^{-3}\) under standard conditions) for the materials, while No. 2 was used to measure emissions from  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Item** & **Fannel** & **Weaved Leather** & **Microfiber Lining** & **Carpet** \\ \hline Estimated age & \textless{}1 year & \textless{}1 year & \textless{}1 year & 1-2 years \\ \hline Pictures & & & & \\ \hline Exposed area, m\({}^{2}\) & 0.091 & 0.088 & 0.080 & 0.064 \\ \hline Thickness, mm & 0.90 & 0.59 & 0.80 & 4.83 \\ \hline Weight, g & 18.327 & 70.514 & 30.727 & 200.065 \\ \hline Density, kg\(\cdot\)m\({}^{-3}\) & 233.8 & 1358.1 & 480.1 & 647.2 \\ \hline Loading ratio, m\({}^{2}\cdot\)m\({}^{-3}\) & 1.62 & 1.79 & 1.84 & 1.30 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Material information on the specimens of the four synthetic fibers.  
the material with low background ozone concentrations (\(<\)10 ppb or \(<\)21.4 \(\mu\)g\(\cdot\)m\({}^{-3}\), i.e., below the detection limit) for comparisons. The same specimen was placed into the two chambers separately for designated testing.  
Two channels of clean air were supplied separately at approximately 1.25 \(\pm\) 0.1 L\(\cdot\)min\({}^{-1}\) (to avoid suck-back when sampling) to the two emission chambers (the ACH was approximately 1.52 h\({}^{-1}\)) using an electromagnetic air compressor (Hailea ACO-009E, 160 W, Guangdong Hailea Group Co., Ltd., Chaozhou, China), a zero-air generator (BCHP ZA-1000, Beijing BCHP Analytical Technology Institute, Beijing, China), and two mass flow controllers (Aera FC-7700 CD, 0-1000 sccm, Advanced Energy Industries, Inc., Fort Collins, CO, USA) in parallel. The clean-gas cylinder was used in the beginning and was replaced by the air compressor and zero-air generator combination due to technical issues. A primary airflow calibrator (MesaLabs Bios Defender 520-M, 50-5000 mL\(\cdot\)min\({}^{-1}\), Mesa Laboratories, Inc., Lakewood, CO, USA) was used to calibrate the flow rate.  
Both emission chambers were stored inside a 1 m\({}^{3}\) environmental chamber to maintain a constant temperature of approximately 23 \({}^{\circ}\)C, which was also measured using high-precision sensors (Vaisala HMP 110, Vaisala Oyj, Vantaa, Finland) at a 1 min interval. In addition, since the air flowrate in the two channels was slow, the air was pre-conditioned to the same temperature as the emission chamber, and the relative humidity (RH) of the air was approximately 20%. All the data on temperature, RH, and flowrate were recorded by a graphical programming platform called ForceControl (V7.0, Beijing ForceCon Yauntong Technology, Beijing, China).  
Figure 1: The laboratory chamber apparatus. (**a**) Environmental chamber. (**b**) Two emission chambers with multiple ports.  
Figure 2: Schematic diagram of the laboratory apparatus for measuring ozone deposition and volatile organic compound (VOC) emissions rates.