# Applicability of Human Thermophysiological Model for Prediction of Thermal Strain in PPE
## 3 Results
### Creating of Predictor of Thermal Stress Tool  
Due to the complexity and difficulty of using the FMTK thermophysiological model, a simpler and more user-friendly computational PTS tool was developed. The core of the PTS computational tool is based on an extensive set of look-up tables created from simulations of 11,664 scenario variants calculated using the FMTK model. The scenarios include different variants of PPE, climatic conditions, work regimes, and activities, as described in Tables 2 and 3. The prediction accuracy of the PTS tool is related to the number of scenarios precomputed. In developing and building the look-up table, it was initially tested with 1920 scenarios, next with 5184, then with 11,664, and finally, with 37,908. After due consideration, the version with 11,664 scenarios was adopted. The user interface of the PTS tool is shown in Figure 8.  
Once all the required input data fields have been selected/entered on the input screen, the PTS tool selects the most-similar combination from the precalculated inputs stored in the locked sheet, and the results are calculated and displayed. The input parameters include six protective ensemble variants; see Figure 9a. The input climatic conditions cover a range of ambient temperatures from 5 \({}^{\circ}\)C to 45 \({}^{\circ}\)C, taking into account relative humidity and wind speed (0.05-2.4 m/s). The presumed metabolic activity of the person performing the activity is an essential input; see Figure 9b. The metabolic activity (0-8.5 met) can be entered as \"measured\" in the case when it is possible to measure directly the energy expenditure using an O\({}_{2}\)/CO\({}_{2}\) analyzer during the tests or other monitoring device or \"tabulated\", which can be selected from the listing of described activities in met units provided in a separate additional data sheet [31]. Based on the individual person parameters such as height (151-200 cm), weight (25-124.9 kg), age (21-70), and sex (male/female), the PTS tool recalculates the entered \"Activity\" in met units into individualized \"Corrected Activity\" in met, which is then used for searching in the look-up tables. The PTS tool has precalculated data for particular input values. When any value within the range is entered, the value is used to find the nearest value in the precalculated table. This retrieved value is displayed in the real inputs (control) graphical interface; see Figure 9b. If out-of-range values are entered, all values are displayed as 0-0-0-0 or a \"Divide by zero\" message is shown in the GUI. Figure 7: Mean absolute error (MAE) of the rectal temperature prediction using the PHS and FMTK models on the air-permeable and impermeable protective ensembles. Figure 8: Predictor of Thermal Stress (PTS) tool–user interface. Figure 9: (**a**) Offer of the PPE ensembles. (**b**) For the combination entered in Figure 8, the input parameters are a 24 \({}^{\circ}\)C ambient temperature, 50% RH, an air velocity of 0.2 m/s, and the expected work intensity activity 4 met corresponding to light-medium manual work or walking with a load of up to 10 kg. For the given individual (40 years, 180 cm and 80 kg), the entered “tabulated” metabolic activity 4.0 met was converted into a “corrected activity” of 4.5 met, corresponding better to the given person. The closest activity value in the precalculated table is 4.8 met; therefore, the value of 4.8 met was used for the following search, as indicated in the purple column in the real inputs (control) field. The entered ambient temperature 24 \({}^{\circ}\)C was corrected to 25 \({}^{\circ}\)C as the nearest temperature covered in the look-up tables. For advanced users, it is possible to set the interpolation between the closest points in the table in the worksheet, making the PTS prediction tool behave like a continuous model. If interpolation is turned on, the desired values are calculated based on a weighted average of the closest scenarios found; typically, this can be the 4-10 closest scenarios.