## 2 Method
### Test Scheme  
The canteen kitchen was divided into four test parts, including the measurement points of the exhaust fume system, the makeup air measurement points, the indoor environment measurement points and the outdoor measurement points. The location of the measuring points in each part of the canteen kitchen is shown in Figure 1.  
1. Measuring points of exhaust fume system: To assess the actual working status of the exhaust fume system, we arranged the measuring points according to the working procedure of the exhaust fume system, including capture point1, oil fume source2, hood face3, air inlet in hood4, discharge outlet5 and system energy consumption6. 2. As shown in Figure 1, point 1 was located at the outer edge of the stoves farthest from the air inlet in the hood to monitor whether it met the minimum air velocity required to capture cooking pollutants into the hood [27]. Point 2 was located at 0.5 m [28] above the stoves to measure the oil fume emission concentration under different cooking styles. Point 3 was located at the hood face to measure the air velocity of the hood face. Measuring point 4 was located at the connecting exhaust hood and air duct to  
Figure 1: Location of measuring points in the canteen kitchen. measure the exhaust airflow rate during the hood working. Point 5 was set at the outdoor discharge outlet to measure the oil fume concentration emitted outdoors. Point 6 was located at the purifying equipment to get the energy consumption of the exhaust fume system. 3. Measuring points of the indoor environment: The measuring points of the indoor environment included cooking zone7 and the indoor area8. We set points 7 at 0.5 m away from the stoves and 1.5 m away from the floor [29] to study the temperature and humidity in the chef's breathing area. According to GB/T18883 [30], for a 70 m\({}^{2}\) kitchen, point 8 should be set with 5 points, which were distributed in quincunx, greater than 0.5 m from the wall, and height 0.5 m-1.0 m.
4. Measuring points of the makeup air system: The measuring points of the natural makeup air9 and the mechanical makeup air10 were considered. Point 9 was located at the door connected to the adjacent room; point 10 was located at the ceiling air outlet. Point 10 was not tested because the mechanical ventilation system was not turned on during the test. 5. Measuring points of the outdoor environment: It was arranged at 0.5 m away from the kitchen exterior wall, 0.8-1.8 m above the ground, and with no direct sunlight. The test schemes of the above four types of measuring points are shown in Table 1.  
Test parameters included air velocity, temperature, humidity, oil fume emission concentration, and energy consumption. In this study, the air velocity and the temperature of the exhaust fume system were measured with hot-wire anemometer. We used a temperature and humidity recorder RC-4 HA/C to measure the temperature and humidity of the indoor area, cooking zone, and makeup air system. EX300 electricity recorder was used to measure the electricity consumption of the kitchen. In order to obtain the oil fume emission concentration, we used the microcomputer oil fume sampler TH-880F(O\({}_{2}\)) to collect five samples in the constant velocity mode at the discharge outlet during the cooking peak hours. Those samples were collected for 10 min [31]. Then, we analyzed those samples according to standard GB18483 [32] to obtain the oil fume concentration. The details of the measuring instruments are shown in Table 2.