## 6 Conclusions  
An experimental outdoor work tent was used to study the thermal comfort of personnel in hot and humid environments. Using the wet bulb globe temperature (WBGT) index, the thermal environment was divided into four working conditions: 21-23 \({}^{\circ}\)C, 23-25 \({}^{\circ}\)C, 25-27 \({}^{\circ}\)C and 27-29 \({}^{\circ}\)C. Changes in physiological parameters of the test personnel were analyzed, and relationships between subjective feelings and physiological parameters of the simulated nucleic acid sampling personnel were investigated. The following main conclusions were drawn:  
(1) When the WBGT index was between 25 and 27 \({}^{\circ}\)C, the human test participants had uncomfortable thermal sensations. When the WBGT index was between 27 and 29 \({}^{\circ}\)C, the test participants' mean skin temperature was between 33.82 and 36.48 \({}^{\circ}\)C, their mean heart rate was 106.12 bpm, their mean sweat production in the test period (one hour) was 135.24 g and their PSI index reached 4.1 (moderate heat strain), all suggesting a relatively high level of discomfort.  
(2) In terms of gender differences, there was no significant difference in \(T_{sk}\) and \(HR\) between male and female samples. There were significant differences in the \(SW_{p}\) and \(M\) between male and female samples (\(p<0.05\)). The mean skin temperature and sweating of the human body were the main factors affecting the subjective voting of participants. The correlation degree between \(T_{sk}\) and TSV and TCV was the most significant (\(p\leq 0.01\)), and the correlation between sweating and HSV was significant (\(p\leq 0.01\)).  
(3) The forehead, chest and back were the three body locations with the highest skin temperature. From the participants' voting of sweating and uncomfortable positions, the forehead, face, neck, chest and back accounted for the highest proportion of discomfort. When the WBGT increased to 27-29 \({}^{\circ}\)C, 100% of the participants expected the external temperature to be cooler and the humidity to be less, with expected values of 0.5-1. This shows that measures must be taken to reduce the temperature and humidity of the human skin surface in order to improve the thermal feeling and comfort of personnel.  
Conceptualization, Y.Z. and J.L.; methodology, J.L.; formal analysis, Y.Z. and J.L.; investigation, Y.Z., J.L., Y.D. and S.Z.; writing--original draft preparation, Y.Z.; writing--review and editing, J.L., M.K.K. and S.Z.; supervision, J.L. and M.K.K.; project administration, J.L. All authors have read and agreed to the published version of the manuscript.  
This work was funded by the Support Plan for Outstanding Youth Innovation Team in Colleges and Universities of Shandong Province (2019 KJG005) and Natural Science Foundation of Shandong Province (ZR2020 ME211, ZR2021 ME199).  
The study was conducted according to the guidelines of the Declaration of Helsinki and approved by the Ethics Committee (represented by Science and Technology Department) of Shandong Jianzhu University (Project: \"Experimental study on thermal comfort of COVID-19 nucleic acid sampling staff in hot and humid environment\", supervised by [PERSON], approved on 16 June 2020).  
Informed Consent Statement: Informed consent was obtained from all subjects involved in the study.  
This work acknowledges the support of the Plan of Introduction and Cultivation for Young Innovative Talents in Colleges and Universities of Shandong Province, as well as the graduate students as participants from Shandong Jianzhu University.  
The authors declare