Heat stress: comparison of short exposure to severe dry and wet heat in saunas

60 subjects: 33 males and 27 females, from 18 to 63 yr of age, were exposed to 2 kinds of saunas: the Finnish sauna (dry sauna) with an air temperature of 80° to 90°C and a relative humidity of 50% and the wet sauna with an air temperature of 45° to 50°C and a relative humidity of 100%. There was a rest period of 1 wk between the 2 experiments. For the 60 subjects the mean duration in the wet sauna was 19.6 min and in the dry sauna it was 17.4 min. After 10 and 20 min of exposure in the wet sauna the mean rectal temperature was 38.1 and 38.5 respectively, the mean skin temperature 40.2 and 40.4°C, the respiratory rate 21 and 22.9 breaths/min., the pulse rate 113 and 135.4 beats/min, the mean diastolic pressure 76.1 and 71.9 mm Hg, and the mean systolic pressure 115.7 and 123.5 mm Hg. Comparing the different physiological parameters in both saunas showed significant differences only during the first 10 min: a greater drop in diastolic blood pressure, and a greater rise in pulse rate in the dry sauna. After 20 min there were no significant differences between any of the above parameters. It is concluded that the heat strain and hence the risk in both saunas are similar and exposure in either sauna exceeding 10 min may be dangerous.