UPPER LIMITS FOR INDOOR AIR HUMIDITY TO AVOID UNCOMFORTABLY HUMID SKIN

The hypothesis that skin humidity in itself could be a cause of discom fort was tested with forty persons exposed to five levels of skin humi dity. In addition, the effect of fabric material against the skin (cot ton versus polyester) and of environmental temperature/clothing insula tion on perceived discomfort was studied at one high level of skin hum idity. Under all experimental conditions, skin humidity was controlled by the combination of vapor permeability of the experimental clothing ensemble and the thermal environment. The subjects perceived the cond ition of their skin to be less acceptable with increasing skin humidit y at thermal neutrality. No effect of clothing material against the sk in or of environmental temperature/clothing insulation was observed. A model was developed that predicts the percentage of persons dissatisf ied due to humid skin as a function of the relative humidity of the sk in. Existing models of heat and mass transfer can predict the relative skin humidity from thermal environmental parameters, clothing and act ivity. The new skin humidity model applies for sedentary, thermally ne utral persons. The model was used to specify upper limits for indoor a ir humidity required to avoid discomfort caused by skin humidity. The model predicts that the relative air humidity may be close to 100% wit hout causing much discomfort from humid skin among thermally neutral p ersons performing sedentary work. (C) 1998 Elsevier Science S.A. All r ights reserved.