It was hypothesized that high skin wettedness and elevated skin temperature would negatively affect psychophysical performance. Twelve volunteers participated in a four-hour experiment in each environmental condition Condition 1 (COND 1): T(sub a) = 28 deg C, 50% rh; Condition 2 (COND 2): T(sub a) = 36 deg C, 50% rh; and Condition 3 (COND 3): T(sub a) = 36 deg C, 75% rh. T(sub c) was significantly higher in COND 2 (37.2 +/- 0.3 deg C) and COND 3 (37.3 +/- 0.3 deg C) compared to COND 1 (36.8 +/- 0.2 deg C) during the four-hour experiments (p < 0.05). Mean skin temperature was lower in COND 1 (32. 4 +/- 0.12 deg C), than COND 2 (35.3 +/- 0.10 deg C) and COND 3 (35.6 +/- 0.13 deg C, p < 0.05). Mean heat flow was higher in COND 1 (57 +/- 2 W), than COND 2(6 +/- 2 W) and COND 3 (11 +/- 5 W, p < 0.05). The thermal comfort and thermal sensation assessments reflected the physiological responses. The subjective index of thermal discomfort effectively discriminated among the environments. The ESQ subjective heat index scores were higher for COND 2 and COND 3 compared to COND 1 (p < 0.05). These subjective responses tracked skin wettedness. Skin wettedness averaged over the entire body surface was related to thermal comfort (R2 = 0.94). This research provided evidence that skin wettedness predicted thermal comfort effectively in all environments tested. The subjective assessment of thermal comfort discriminated between all environments and the heat index derived from the USARIEM Environmental Symptoms Questionnaire discriminated between the neutral and the two hot environments. Unfortunately, several indices derived from the Environmental Symptoms Questionnaire had limited utility to discriminate among significantly different environments.
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