# Infrared Thermography to Evaluate Thermal Comfort under Controlled Ambient Conditions
## 5 Conclusions  
This work has allowed a better understanding of several issues related to the measurement of face temperatures using IRT. It shows that face temperatures are more heterogeneous at lower air temperatures and the thermal patterns become more homogeneous above 26 \({}^{\circ}\)C. On the other hand, there are no evident impacts of the relative humidity on the temperature of the face, nor on its thermal patterns. The core temperature, as measured by the contact thermometer, was consistently higher than the one measured with the IR cameras, which was expected. However, the results also confirmed the reliability and consistency of the measurements carried out using IRT.  
Regarding the results obtained with the two IR cameras, they were similar in terms of the qualitative analysis but were more clearly marked in the images where the face was more centrally framed. Furthermore, the position of the hottest point on the face pointed to a statistically significant association when assessed with the two IR cameras. From these results, the maximum temperatures on the face as measured by the two IR cameras were statistically different, pointing to an impact of the camera position.  
The hottest points on the face were mostly located in the mouth, followed by the eyes and forehead. The lower temperatures always occurred on the nose, but the differences from the other subregions tended to attenuate when the air temperature increased. The average facial temperature can be used as an indicator for the determination of the face temperature, while an evaluation of the individual subregions is unnecessary, which indicates that it can be used as a parameter for the determination of thermal comfort.  
A strong relation was found between the PMV and the temperature of the entire face (R\({}^{2}\) = 93.3%), which allowed us to establish an innovative prediction model for PMV based on the IRT results. The model presented a root mean square error close to 0.70 when applied  
Figure 12: PMV prediction model as a function of the average face temperature.  
in a face temperature range between 28.9 \({}^{\circ}\)C and 34.4 \({}^{\circ}\)C. The encouraging results that were produced by this work will enable us to proceed to the next stage, which will involve the generalization of the model by increasing the size of the sample and including aspects such as the type of skin, age, gender, and weight, which will allow us to fine-tune its accuracy. By expanding the sample size, special attention can be paid to the impacts of gender and age, which are typically pointed out as factors that influence the perception of comfort. The airflow and the view angle of the IRT camera are also possible sources of uncertainty that must be taken into consideration in the following steps of the research. Afterwards, the validation of the model must be carried out in real environmental conditions.  
Conceptualization, R.M.S.F.A. and E.B.; methodology, R.M.S.F.A. and E.B.; formal analysis, R.M.S.F.A., E.B., M.L.S. and T.S.F.S.; resources, R.M.S.F.A. and E.B.; data curation, M.L.S. and T.S.F.S.; writing--original draft preparation, T.S.F.S.; writing--review and editing, R.M.S.F.A., E.B. and M.L.S. All authors have read and agreed to the published version of the manuscript.  
This work was financially supported by Base Funding UIDB/04708/2020 of the CONSTUCT Instituto de I and D em Estruturas e Construcoes, funded by national funds through FCT/MCTES (PIDDAC), and by the \"Protocolo de medicao da temperatura corporal atraves da termografia de infravermellos--IRT4 COVID19\" research project under the scope of \"Apoios Especiais do Instituto Politecnico de Viseu, despacho n\({}^{\circ}\) 59/2020 de 15-09-2020\".  
Not applicable.  
Informed Consent Statement: Informed consent was obtained from all subjects involved in the study.  
Not applicable.  
The authors declare no conflict of interest.