2007, Piran, Slovenia

Environmental Ergonomics XII
Igor B. Mekjavic, Stelios N. Kounalakis & Nigel A.S. Taylor (Eds.), © BIOMED, Ljubljana 2007
separately and altogether before and after the tests. Metabolic rate was determined by
measuring VO2 for 5-9 minutes between 10 th and 20 th minutes of walking on the
treadmill. Thermal responses were obtained at each 10 th minute.
Weight (g)
170
500
400
300
200
100
0
-100
-200
-300
Weight loss through sweating Total accumulation Evaporative water loss
All data are corrected for respiratory water loss
IMP10D IMP10W IMP25D IMP25W PERM10D PERM10W PERM25D PERM25W
Figure 1. Weight change through sweating, accumulation and evaporation.
RESULTS AND DISCUSSION
Energy production was 168±19 W/m 2 . In wet tests the metabolic rate was in average 8
W/m 2 higher than in dry tests. It may be related to higher friction in clothes,
discomfort etc. Figure 1 shows weight loss through sweating, moisture gain/loss in
and evaporation from the clothing system. Negative accumulation values correspond
to higher evaporation than generated by sweating. As expected, accumulation was
higher in impermeable coverall. Sweating was lower in cool environment and with
wet underwear. In cool environment sweating was at about the same level for both
permeable and impermeable clothing. Wet underwear lowered the sweat production at
10 °C. It reduced sweating considerably in warm environment in permeable, but not
in impermeable overall coverall. All conditions with permeable overall coverall
showed lower Tsk than corresponding conditions with impermeable one, and all wet
conditions had lower Tsk than dry conditions. The lowest Tsk was observed in
PERM10W and next lowest in IMP10W (Figure 2). Tsk in PERM10W was the lowest
probably due to high evaporation, while in IMP10W mass loss was minimal (Figures
1 and 2). The highest Tsk was observed in IMP25D followed by PERM25D and
IMP25W. In latter case the initial cooling power of moisture and later heat
accumulation could be observed. Dry conditions at 10 °C behaved similarly. Trec kept
growing in most conditions up to the end of the test. The rise (mean increase 0.3 °C/h
for all conditions) just slowed down. In 2 wet conditions at +10 °C Trec stopped
growing and even began decreasing in permeable overall coverall (PERM10W).
However, the mean difference in ∆Trec by the end of the exposure was 0.15 °C
between the warmest and the coolest condition. Thus, the observable differences in Tb
were dominated by changes in Tsk. Tb kept increasing at 25 °C in impermeable overall
coveralls (wet and dry). It kept only very slightly decreasing in 2 wet conditions at 10
°C. All conditions with permeable overall coverall showed lower Tb than those with
impermeable one, and all wet conditions had lower Tb than dry conditions (Figure 3).
The lowest Tb was observed in PERM10W and next lowest in IMP10W. The highest
Tb was observed in IMP25D followed by IMP25W and PERM25D. Dry conditions at
10 °C behaved similarly. It can be seen that the evaporative cooling from wet