2007, Piran, Slovenia

Working Environment
responses between the conditions involving 2 versus 6 occupants: the data were therefore
pooled for the statistical analysis. At the end of the 135 min exposures, Tsk was significantly
lower for all conditions (Udry: 32.1±0.7°C; Uwet: 30.0±1.0°C; Iwet: 30.9±1.1°C) except for
Idry (33.5±0.8°C). Heat loss, however, increased significantly only for the wet conditions
(Uwet: 67.4±11.2 W/m 2 ; Iwet: 64.9±11.0 W/m 2 ), and stayed constant for the dry conditions
(Udry: 55.8±8.9 W/m 2 ; Idry: 52.4±5.1 W/m 2 ). Tre decreased in all conditions but
significantly more during the uninflated conditions (mean decrease of 1.1±0.5°C; Udry:
36.0±0.6°C; Uwet: 36.0±0.6°C) when compared to the inflated conditions (mean decrease of
0.7±0.3°C; Idry: 36.4±0.4°C; Iwet: 36.5±0.4°C). The wetness of the clothing had no
significant effect on the magnitude of the core temperature cooling despite a significant
increase in heat loss. Furthermore, despite the absence of a significant increase in heat loss
during the dry conditions when compared to baseline, Tre significantly decreased by
1.1±0.5°C for the Udry condition and by 0.7±0.3°C during the Idry condition. The average
metabolic rates of the subjects during the exposures were not different between conditions
(Udry: 117.6±9.0 W; Uwet: 131.8±9.6 W; Idry: 111.04±9.0 W; Iwet: 122.0±8.4 W) despite
some intermittent shivering and tremor observed for some subjects near the end of the
exposures for condition Uwet. A similar trend was observed when the data were expressed in
W/kg (Udry: 1.42±0.11 W/kg; Uwet: 1.65±0.11 W; Idry: 1.46±0.11 W; Iwet: 1.63±0.10 W).
There was, however, a tendency for an increase in M for the wet and uninflated conditions.
DISCUSSION
The present study showed that even during exposure to mild cold environments inside a
closed liferaft, the wetness of the clothing worn by the occupants and the absence of floor
insulation will both significantly decrease the mean skin temperatures of the occupants while
only the wetness of the clothing will increase the heat loss from the subjects. However, the
thermal stress imposed by the different conditions tested was not sufficient to significantly
and consistently increase the metabolic rate of the occupants through shivering. Despite the
mild responses to cold during the exposures (Tsk above 30°C, HF increased by < 15%; no
definitive shivering), Tre significantly decreased for all conditions tested by as much as
1.1°C. This was particularly the case for the condition Udry where the Tsk was on average
32°C by the end of the exposure, and both HF and M had not increased from baseline. If the
observed rate of decrease in Tre for that condition is extrapolated, it could be predicted that
the occupants would not survive for more than 18 hours inside a liferaft originally designed
for a multi-days survival in much colder environments. It is concluded that to estimate
survival time inside a liferaft, or to evaluate the thermal protection of a liferaft, the short-term
decrease in Tre from the occupants should not be the only or primary factor taken into
consideration.
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