# Infrared Thermography to Evaluate Thermal Comfort under Controlled Ambient Conditions
## 2 Framework
### Experimental Campaign  
In the experimental campaign, the face temperature of a 24-year-old male was assessed using IRT and the emissivity of the skin was 0.98 [17]. To evaluate the influence of the ambient conditions, several scenarios were created. To this end, the air temperatures varied between 10 \({}^{\circ}\)C and 30 \({}^{\circ}\)C, with increments of 2 \({}^{\circ}\)C, while the relative humidity values varied between 40% and 80%, with increments of 5%, leading to a total of 99 different combinations of ambient conditions. The inputs in the climatic chamber were designated as the T\({}_{\rm SP}\) (temperature setpoint) and RH\({}_{\rm SP}\) (relative humidity setpoint).  
Figure 1 shows a schematic representation of the setup inside the climatic chamber, showing the position of the equipment and the location of the individual. The inner metallic surfaces of the climatic chamber were covered with black canvas to prevent reflection problems. The limitations of the space inside the climatic chamber resulted in a different framing of the head of the individual in the images taken by each IR camera.  
The experimental procedure implemented for each scenario is schematically represented in Figure 2. The full duration of each test was approximately 50 min. The procedure started with the programming of the climatic chamber with the setpoint conditions (T\({}_{\rm SP}\) and RH\({}_{\rm SP}\)), followed by the stabilization of the indoor environment for approximately 30 min. After that period, the individual under study entered the climatic chamber, initiating the acclimatization process, which took about 10 min. During that period, the necessary calibrations of the IR cameras and the assessment of the reflected temperature,  
\begin{table}
\begin{tabular}{c c c} \hline \hline  & **IR Camera 1** & **IR Camera 2** \\ \hline Temperature range & \(-20\)\({}^{\circ}\)C to \(100\)\({}^{\circ}\)C & \(-20\)\({}^{\circ}\)C to \(400\)\({}^{\circ}\)C \\ Accuracy & \(\pm 2\)\({}^{\circ}\)C or \(2\)\% & \(\pm 2\)\({}^{\circ}\)C or \(2\)\% \\ Thermal sensitivity & 0.06 \({}^{\circ}\)C at \(30\)\({}^{\circ}\)C & \(\leq\)0.045 \({}^{\circ}\)C at \(30\)\({}^{\circ}\)C \\ IFOV & 1.2 mrad & 1.86 mrad \\ Infrared resolution & \(320\times 240\) pixels & \(320\times 240\) pixels \\ Field of view & \(20.1^{\circ}\times 22.7^{\circ}\) & \(34.1^{\circ}\)H \(\times 25.6^{\circ}\)H \\ Minimum focus distance & 30 cm & \(<\)46 cm \\ Infrared spectral range & 8 to 14 \(\mu\)m & 7.5 to 14 \(\mu\)m \\ \hline \hline \end{tabular}
\end{table}
Table 1: IR camera characteristics.  
Figure 1: Schematic representation of the setup inside the climatic chamber.  
through the procedure described in the standard ASTM: E 1862-97 [25], were conducted. The reflected temperature is the temperature of the energy incident upon and reflected from the surface under study, which can cause measurement errors if not considered and compensated for during data treatment [26]. Finally, the thermal image was captured through an automatic procedure.  
Since the range of the temperature setpoints was substantial [10 \({}^{\circ}\)C \(\leq\) T\({}_{\text{SP}}\)\(\leq\) 30 \({}^{\circ}\)C], the individual's clothing was adapted to the T\({}_{\text{SP}}\). This adaptation process targeted the chest area as follows: (i) T\({}_{\text{SP}}\): 10 \({}^{\circ}\)C to 14 \({}^{\circ}\)C, t-shirt + sweater + coat; (ii) T\({}_{\text{SP}}\): 16 \({}^{\circ}\)C to 24 \({}^{\circ}\)C, t-shirt + sweater; (iii) T\({}_{\text{SP}}\): 26 \({}^{\circ}\)C to 30 \({}^{\circ}\)C, t-shirt.  
Additionally, the measurements of the core temperature using the thermometers were carried out for the RH\({}_{\text{SP}}\) 40%, 60%, and 80% conditions. The measurements occurred after the acclimatization period of 10 min, immediately before capturing the thermal images. The contact thermometer measured the temperature inside the mouth and the non-contact thermometer measured the temperature in the center of the forehead.