Page 232 - Industrial Ventilation Design Guidebook

REFERENCES 1 93

FIGURE 5.13 Perceived skin moisture correlated to measure skin wettedness for activities from I
to 3 met.

duced, increasing susceptibility to respiratory disease as well as discomfort.
27
Green quantified that respiratory illness and absenteeism increase in winter
with decreasing humidity. He found that any increase in humidity from the
low winter levels decreased absenteeism. Excessive drying of the skin can lead
to lesions, skin roughness, and discomfort and impair the skin's protective
functions. Dusty environments can further exacerbate low-humidity dry skin
conditions. 28
29
Liviana et al. found that drying from low humidity can contribute to eye
irritation. Eye discomfort increased with time in low-humidity environments
T dp < 2 °C.

High Humidity
30
Comfort is reduced by elevated humidity levels. It is recommended that
on the warm side of the comfort zone the relative humidity should not exceed
60% to prevent warm discomfort. On the cool side of the comfort zone, high
humidity is less important because there is no sweating to increase skin mois-
ture. For these reasons the upper boundaries of comfort zones in Fig. 5.7b are
wet bulb temperatures of 18 and 20 °C for the winter and summer comfort
zones respectively.

References
1. Langlulde, G., Alexandersen, K., Wyon, D. P., and Fanger, P. O. (1973). Mental performance during
slight cool and slight warm discomfort. Archives Des Sciences Physiologiques 27, 511-518,
2. Macworth, N. H. (1946). Effects of heat on wireless operators hearing and recording Morse
Code messages. Brit. J. Ind. Med., 3:143-158.
3. Vernon, H. M. (1948). An investigation of the factors concerned in the causation of industrial
accidents. In Basic Principles of Ventilating and Heating. T. Bedford, Lewis & Co., p. 346,