# Applicability of Human Thermophysiological Model for Prediction of Thermal Strain in PPE
## 2 Materials and Methods
### Thermal Insulation Characteristics of the Clothing  
The thermal insulation characteristics of the clothing were measured in a climatic chamber at Brno University of Technology using the 34-zone Thermal manikin Newton (Theremetrics, Seattle, WA, USA).  
The total thermal insulation of clothing \(I_{T}\) and local thermal insulation \(I_{T,i}\) were measured using a standard procedure according to EN ISO 15831 [26] and calculated according to Equations (1) and (2). The evaporative resistance \(R_{eT}\) was measured using a non-standard method based on the measurement of moisture loss from the \"artificial skin\" covering the entire surface of the manikin [27] and recalculated from the measured heat loss according to Equation (3) [27].  
For further purposes of the data input of \(I_{T}\), we used clo units instead of m\({}^{2}\cdot\)K\(\cdot\)W\({}^{-1}\), where 1 clo = 0.155 m\({}^{2}\cdot\)K\(\cdot\)W\({}^{-1}\). \(I_{cl}\) is the intrinsic insulation from the skin surface to the outer clothing surface (including enclosed air layers) [28]; \(I_{T}=I_{cl}+I_{a}\), where \(I_{a}\) is the thermal resistance of the outer air layer; for a naked man, \(I_{cl}\) = 0 clo.  
\[I_{T}=\frac{(T_{S}\ -\ T_{a})\times A_{M}}{H_{c}} \tag{1}\]  
\(I_{T}\)--Total thermal insulation including the air boundary layer of the measured garment (m\({}^{2}\cdot\)K\(\cdot\)W\({}^{-1}\));  
\(T_{S}\)--Average manikin surface temperature (\({}^{\circ}\)C);  
\(T_{a}\)--Air temperature in the climatic chamber (\({}^{\circ}\)C);  
\(A_{M}\)--Total body surface area of the manikin (m\({}^{2}\));  
\(H_{c}\)--Total thermal energy delivered to the manikin (W).  
\[I_{T,i}=\frac{(T_{S,i}\ -\ T_{a})\times A_{M,i}}{H_{c,i}} \tag{2}\]  
\(I_{T,i}\)--Local thermal insulation including the air boundary layer of the measured garment (m\({}^{2}\cdot\)K\(\cdot\)W\({}^{-1}\));  
\(T_{S,i}\)--Local manikin surface temperature (\({}^{\circ}\)C);  
\(A_{M,i}\)--Surface area of the individual zones of the manikin's body (m\({}^{2}\));  
\(H_{c,i}\)--Local thermal energy delivered to a given zone on the manikin (W).  
\[R_{eT}=\frac{\Delta\ p_{iso}\times A_{S}}{H_{c}} \tag{3}\]  
\(R_{eT}\)--Total evaporative resistance (kPa-m\({}^{2}\cdot\)W\({}^{-1}\));  
\(\Delta p_{iso}\)--The difference between the saturated vapor pressure at the manikin surface and the ambient vapor pressure (kPa);  
Figure 1: Protective ensembles tested.  
\(H_{e}\)--Amount of evaporative losses from the manikin surface (W);  
\(A_{S}\)--Sweating surface of the manikin (m\({}^{2}\)).  
Based on the measured values of \(I_{T}\) and \(R_{eT}\), the static clothing permeability index \(i_{m}\) was calculated according to Equation (4) described in the standard EN ISO 9920 [28] for all measured types of protective ensembles. In the recalculation of the \(i_{m}\) value, however, it is necessary to take into account a certain uncertainty in the measurement [27; 29].  
\[i_{m}=\frac{I_{T}}{LR\times R_{eT}} \tag{4}\]  
\(i_{m}\)--Static clothing permeability index (-);  
\(LR\)--Lewis constant (\(LR\) = 16.5 K\(\cdot\)kPa\({}^{-1}\)).