## 3 Results and Analysis of the Filed Measurements
### Indoor Environment of Canteen Kitchen  
#### 3.2.1 Seasonal Variation of the Temperature and Relative Humidity  
From Figure 3a, the temperature of the cooking zone was higher than that of the indoor area and outdoor. The annual variation range of the temperature in the cooking zone was 16.70 \(\pm\) 0.30-41.81 \(\pm\) 0.36 \({}^{\circ}\)C, and the highest temperature was 31.53 \(\pm\) 0.31-41.81 \(\pm\) 0.36 \({}^{\circ}\)C in summer, which was 2.50 \(\pm\) 0.75-8.49 \(\pm\) 0.83 \({}^{\circ}\)C higher than that in the indoor area. Contrary to temperature, the relative humidity in the cooking zone was lower than that in the indoor area and outdoors. It can be seen from the Figure 3b that the annual variation range of the relative humidity in the cooking zone was 24.20 \(\pm\) 1.76-59.17 \(\pm\) 2.71%RH, which was 4.00 \(\pm\) 4.04-20.64 \(\pm\) 3.99%RH lower than that in the indoor area. According to BEN16282 [18], the comfortable range of the indoor temperature and the relative humidity in the breathing zone (breathing zone: at the height of 1.1 m above the floor at a distance of 0.5 m from the stoves) in commercial kitchens was 18-26 \({}^{\circ}\)C and 30-65%RH, respectively. The tolerance range was 26-32 \({}^{\circ}\)C and 65-80%RH, respectively. The data showed that the temperature in the cooking zone of the canteen kitchen was above the acceptable range (18-32 \({}^{\circ}\)C) in late spring, summer, and early autumn. It may be because the indoor environment of the canteen kitchen was highly dependent on the outdoor environment [34], and the waste heat cannot be effectively removed without the installation of an air-conditioning air supply system. It was necessary to explain that the breathing zone height specified in BEN16282 was 1.1 m. Considering the height difference of the chefs \begin{table}
\begin{tabular}{c c c} \hline \hline  & **Number of Chefs** & **Percentage (\%)** \\ \hline  & Gender & \\ Male & 27 & 75.00 \\ Female & 9 & 25.00 \\ Age & & \\
16–20 & 9 & 25.00 \\
21–30 & 16 & 44.44 \\
31–40 & 5 & 13.89 \\ \(\geq\)41 & 6 & 16.67 \\  & Right (cm) & \\
150–160 & 7 & 19.44 \\
161–170 & 14 & 38.89 \\
171–180 & 14 & 38.89 \\ \(\geq\)181 & 1 & 2.78 \\ \hline \hline \end{tabular} Note: The chefs participating in cooking activities are all male, and they are above 160 cm.  
\end{table} 
Table 3: Basic information about chefs. in different regions, the height of the breathing zone in this study was selected according to GB/T18883 [30], which recommended 0.5-1.5 m. In the indoor area, the height of the vegetable shelf was 1.0 m, and the height of the breathing zone when chefs took vegetables should be about 1.0 m. In the cooking zone, the breathing zone should be at 1.5 m when chefs are standing. Figure 2: The usage status of stoves and the situation of chefs standing in front of the stoves on a typical test day. To analyze the annual variation of canteen kitchen temperature and relative humidity quantitatively. The seasonal variation of the temperature and relative humidity in different comfort ranges at different measurement points during working hours (6:40-13:40; 15:00-20:00) is shown in Figure 4.  
Figure 4a shows that the comfort range of the temperature varies with seasons. The temperature distribution in spring and autumn were similar, with 64.88% and 76.92% of the working time in the cooking zone being in the acceptable range (18-32 \({}^{\circ}\)C), respectively. In the indoor area, 98.41% and 86.17% of the working time were in this range, respectively. The temperature in the cooking zone was the highest in summer. 82.92% of the working hours were above the acceptable range. In winter, 57.73% and 97.57% of the working time in the cooking zone and indoor area, respectively, were below the comfort range (18-26 \({}^{\circ}\)C). From Figure 4b, the relative humidity was in the comfortable range (30-65%RH) during most of the working time in the four seasons. For the indoor area in summer, 50.48% of the working time was within the tolerance range (30-80%RH).