**1. Introduction**

According to previous research regarding building fires, the main factor contributing to human casualties is the dispersion of smoke through building openings [1]. The mortality rate due to this is over 50% greater than the mortality rate due to causes directly related to fires [2], which is why the smoke control performance of building openings has particular importance. Currently, the smoke control performance of building doors has been specified in various countries [3–9], requiring qualified smoke control doors to provide smoke control capabilities under both medium-temperature and ambient-temperature conditions. As a consequence of the complexity of fire scenarios, ambient-temperature smoke may also be life threatening [10]. For example, if a source of fire is relatively distant from a door, the temperature of the smoke near the door may be relatively low or even comparable to ambient temperatures. In such a scenario, while the door may not be damaged by the heat of the fire, individuals on the rear side of the door may be fatally exposed to excessive smoke inhalation. Therefore, a door's fire protection effectiveness may not be the primary concern. Instead, what is necessary is the door's capability of resisting against smoke inflow at ambient temperatures and under certain pressures. One example is BS 476-31 [11], which only requires smoke control performance at ambient temperature conditions. Doors with better smoke control capabilities at ambient temperatures can also prevent other toxic gases from entering the interior space under different circumstances, reducing the occurrence of related disasters.

**Citation:** Hung, H.-Y.; Lin, C.-Y.; Chuang, Y.-J.; Luan, C.-P. Application Development of Smoke Leakage Test Apparatus for Door Sets in the Field. *Fire* **2022**, *5*, 12. https://doi.org/ 10.3390/fire5010012

Academic Editors: Chuangang Fan and Dahai Qi

Received: 10 December 2021 Accepted: 15 January 2022 Published: 18 January 2022

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**Copyright:** © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). *fire*

According to Chuang et al. [12,13], Wu et al. [14], Tsai et al. [15], Gross [16], and Kuo et al. [17], under the same differential pressure conditions, when the temperature of the air increases, the volume increases and its density relatively decreases. As a result, the volume leakage of the air through the gap of the door will be reduced. In other words, if the volume of air leakage through the test body gap at ambient temperatures is available, identification whether the smoke control performance of the test subject at medium temperatures can meet the requirements of national regulations can be achieved, provided there is no deformation or damage of the material at medium temperatures. However, the components of doors for architectural use not only consist of steel, but also wood and organic materials, aluminum alloys, or plastics, as well as the use of filler strips, expansion materials, and glass windows. In 2000, Rakic [18] studied the effects of the presence and absence of filler strips on the smoke control performance of doors by means of UL 1784 [9]. The conclusion is that the installation of filler strips in doors could effectively increase their smoke control performance, demonstrating that filler strips and the methods used for the construction of door seams are the key to smoke control performance. However, these materials may be affected by thermal and physical or chemical transformations at medium temperatures, which may lead to inflation, flaming, or glass breakage. Therefore, medium-temperature testing is essential as this step of testing reveals the conditions of heat-induced deformation and damage to materials. To pass the test, the materials must possess capability of withstanding medium temperatures. Therefore, the premise of this field test method was that the test door should first pass the CNS 15038 [3] or ISO 5925- 1 test [5] in the laboratory. The field test should only be conducted at ambient temperatures to determine whether the materials and methods applied can meet practical smoke control performance, so that the smoke control performance of doors tested in the laboratory and doors installed in the field can be realized without any discrepancy. In summary, we have developed a test method for the smoke control capabilities of door sets in the field through testing and theoretical analysis. In the past, the detection method could only be used in the laboratory, and the detection equipment could not be moved. The instrument developed by this research is light and easy to carry, and the operation method is simple. Such a test method can be applied to any doors and is non-destructive, non-hazardous, and reusable, enabling an immediate understanding of the door's smoke control performance in the field. In the future, by extending the design principle of the system, the test method can also be applied to other fire protection equipment for the inspection of smoke control capabilities and can be used as a reference for relevant organizations to establish test specifications and standards. This study offers the designs and descriptions of the equipment utilized with the intention of sharing this information for future reference.
