Too Hot to Handle? An Investigation Into Safe Touch Temperatures

Thermal burns occur when tissue temperature rises above a threshold value for a finite period of time. The safe touch temperature (STT) is the maximum allowable surface temperature for a material at which no tissue damage or pain occurs when the material is touched for a long enough period to allow safe handling. Current guidelines for the determination of safe touch temperatures are limited. The objective of this study was to determine the effect of material type and thickness on the safe touch temperature. We considered two boundary conditions in our evaluation of safe touch temperatures. Case 1 employed a fixed surface temperature on the surface opposite the contact point (i.e. a single sided contact situation like that encountered touching a pipe carrying a hot fluid) and Case 2 employed an adiabatic surface on the surface opposite the contact point (i.e. a two sided contact situation like that encountered when picking up a hot plate). The study utilized a finite element model to predict skin contact temperature as a function of plate temperature for copper and plastic plates ranging in thickness from 0.1 to 3.0 mm. We applied the damage function model of Xu and Qian [1] and determined that for the single sided contact condition the safe touch temperature increases with thickness from a low of 60 °C to a high of 115 °C for plastic and is invariant with thickness for copper at 60 °C. For the two sided contact condition the safe touch temperature was found to decrease as thickness increases from a high of 160 °C to a low of 110 °C for plastic and a high of 100 °C to a low of 60 °C for copper.