*3.1. Confirmation of Device Function*

The precision instruments applied for testing purposes mainly involve a gas volume flow meter, a differential pressure meter, and a blowing engine, and all three of them should be calibrated. Upon completion of calibration, the measured results should be theoretically accurate provided that the equipment is not subjected to impacts. However, since this equipment is used in field tests, it is inevitable that there will be vibrations due to the frequent transportation. Therefore, before each official test, it is necessary to confirm the accuracy of the instrument to maintain the credibility of the test results. As a result, this study designed a test tube to be used for verification prior to official testing (with an inner diameter of 15.24 cm, a length of 100 cm, and a 2 cm diameter round hole in the center of one end of the tube for differential pressure measurement, with the other end connected to an air supply tube). Compare the theoretically calculated volume leakage value with the volume flow value measured by the test tube to confirm the accuracy of the flow meter measurement results. According to theoretical and practical studies in fluid mechanics, the flow coefficient is generally between 0.6 and 0.7 [14]. The different flow coefficients directly affect the calculated value of the flow in the openings. The factors determining the flow coefficients are complex, as the flow coefficients may be influenced by obstructions at the openings, such as the manner in which smoke flows through the openings [24] or the influence of human positioning [25], as well as varying gap widths [13]. For the sake of discussion, the theoretical volume leakage values can be calculated by Bernoulli's equation [26], as shown in Equation (1), assuming a flow coefficient of 0.6 to 0.7, an air temperature of 25 ◦C, and pressure differences of 10, 25, and 50 Pa.

$$\mathbf{Q} = \mathbf{C} \times \mathbf{A} \sqrt{\frac{2\Delta \mathbf{P}}{\rho}} \tag{1}$$

Q: Volume flow rate of air flow through apertures (m3/s);

C: Flow coefficient (C = 0.6~0.7);

A: Flow area or ventilated area (m2/s);

∆P Differential pressure between the two sides of the air flow course (Pa);

*ρ*: Density of air entering the flow course (kg/m<sup>3</sup> ), *ρ* = 352.8 273+*T*∞ ;

*T*∞: Air temperature (◦C).

The calculated leakage values are shown in Table 1, where the volume leakage amounts were 2.79, 4.41, and 6.24 m3/h for pressure differences of 10, 25, and 50 Pa, respectively, at a flow coefficient of 0.6; then, the volume leakage amounts were 3.33, 5.27, and 7.46 m3/h for pressure differences of 10, 25, and 50 Pa, respectively, at a flow coefficient of 0.7. In the future, if the measured volume leakage value is within the theoretical range of 0.60 to

0.70 flow coefficient, the volume leakage measurement equipment can be considered to be good and ready to be applied to the volume leakage measurement of subsequent doors.


**Table 1.** Theoretically projected volume leakage values.
