Upper acceptable surface temperature for prolonged hand contact

One aspect of work in hot environments is that the surfaces of tools, equipment and other elements in the work space can range from warm to very hot. While recommended limits exist to avoid burns or other painful responses to momentary contact with hot surfaces, limits for prolonged contact have not been addressed. To determine experimentally an upper acceptable temperature limit, a psychophysical model was used to relate perceived warmth to surface temperature. The parameters of the model were estimated from experimental data and an upper acceptable surface temperature, T ∗ , was determined. T ∗ depends on surface type (between wood and aluminum). The average value of T ∗ among subjects was 40°C for aluminum and 42°C for wood, and the recommended lower limit for 95% acceptability is 38°C. A relatively small change of 1°C in surface temperature was enough to radically change the sensation of warmth from moderate to the upper acceptable limit.