# Infrared Thermography to Evaluate Thermal Comfort under Controlled Ambient Conditions
## 3 Results of Phase I: IR Camera Comparison  
### Qualitative Analysis  
The qualitative analysis exposed different thermal patterns throughout the experiment, highlighting the impacts of the ambient conditions on the face temperatures, as presented in Figure 4. By analyzing the evolution of the face temperatures with the increase in \(\mathrm{T_{SP}}\), the thermal images show that for lower \(\mathrm{T_{SP}}\) values, the temperatures are more heterogeneous, with the nose and cheekbones being the coldest regions and the mouth and the inner corner eye being the hottest regions. As the \(\mathrm{T_{SP}}\) increases, the nose displays the largest temperature variation, followed by the cheekbones, which exhibit similar values on both sides. The forehead also displays high temperature values, especially at the extremities. Quite unexpectedly, the chin region also displays a high temperature, identical to the forehead, which is related to the use of a face mask (due to COVID-19 restrictions) during the intervals between the different tested scenarios, which is in line with the results found by [PERSON] and [PERSON] [26]. For higher \(\mathrm{T_{SP}}\) values, the face temperatures become more homogeneous, with little difference between distinct regions. This increased homogeneity occurs approximately when the \(\mathrm{T_{SP}}\) reaches 26 \({}^{\circ}\)C. Similar results were reported by [PERSON] et al. [12]. On the other hand, Figure 5 shows that there is no evident impact of \(\mathrm{RH_{SP}}\) in the results, as for the same \(\mathrm{T_{SP}}\) value, the thermal patterns are identical. The findings of the qualitative analysis are visible in the images captured with both IR cameras, even in the ones obtained with IR camera 2, which were not centrally framed.  
The reflected temperatures assessed by each IR camera (T\({}_{\text{ref1}}\)--reflected temperature measured with IR camera 1; T\({}_{\text{ref2}}\)--reflected temperature measured with IR camera 2) presents similar intervals ranges, with slightly higher values being measured by IR camera 1; (b) IR camera 2.  
Figure 4: Thermal images for T\({}_{\text{SP}}\) values of 10 \({}^{\circ}\)C, 16 \({}^{\circ}\)C, 20 \({}^{\circ}\)C, 24 \({}^{\circ}\)C, and 30 \({}^{\circ}\)C with an HR\({}_{\text{SP}}\) of 60%: (**a**) IR camera 1; (**b**) IR camera 2.  
Figure 5: Thermal images for HR\({}_{\text{SP}}\) values of 40%, 50%, 60%, 70%, and 80% with a T\({}_{\text{SP}}\) of 20 \({}^{\circ}\)C: (**a**) IR camera 1; (**b**) IR camera 2.  
Figure 6: Box plots representations of (**a**) temperature and (**b**) relative humidity.  
2. Overall, the average values of the reflected temperatures are identical to the T\({}_{\rm amb}\) values; therefore, one can conclude that the impact of reflection was successfully minimized.  
Figure 7 presents the distribution of the temperatures measured using the thermometers and the maximum temperature obtained using IRT. The results show that the core temperature (measured by the contact thermometer) is consistently higher than those measured by the other devices. The variability of the results attained with the contact thermometer is considerably lower, confirming the higher reliability of the measurements carried out with this device. Although operating based on the same physical principles, the non-contact thermometer presents higher variability than the IR cameras. The maximum temperature measured by IR camera 2 is always higher than the values obtained with IR camera 1. The \(t\)-test confirmed the statistically significant differences between the 2 IR cameras (\(t\)-test = 4.248; \(p\)-value < 0.01%). This result points to a possible impact of the camera position.