2007, Piran, Slovenia

Environmental Ergonomics XII
Igor B. Mekjavic, Stelios N. Kounalakis & Nigel A.S. Taylor (Eds.), © BIOMED, Ljubljana 2007
EFFECT OF WETNESS AND FLOOR INSULATION ON THE
THERMAL RESPONSES DURING COLD EXPOSURE IN A LIFERAFT
Michel B. DuCharme 1 , Kerry-Ann Evely 2 , Fabien Basset 2 , Scott N. MacKinnon 2 , Andrew
Kuczora 3 , James Boone 4 , Lawrence Mak 3
1 Defence R&D Canada, Quebec City, Quebec, Canada, G3J 1X5
2 Memorial University, St. John’s, Newfoundland, Canada, A1C 5S7
3 National Research Council Canada, Institute for Ocean Technology, St. John’s,
Newfoundland, Canada, A1B 3T5
4 Offshore Safety and Survival Centre, St. John’s, Newfoundland, Canada, A1C 5R3
Contact person: michel.ducharme@drdc-rddc.gc.ca
INTRODUCTION
A typical passenger may be wearing little protective clothing during an evacuation from a
seagoing vessel, resulting in the liferaft providing the only significant thermal protection
against the cold environment. While regulatory agencies often require commercial liferafts to
provide thermal protection within its design, there exists limited guidance regarding the
amount of protection needed. The aim of the present study was to characterize the thermal
responses of lightly dressed subjects exposed to mild cold conditions in a liferaft when two
factors affecting heat transfer were modified: the floor insulation of the liferaft and the
wetness of the occupants. This study is part of a larger investigation looking at the thermal
requirement for long-term survival in various sea environments.
METHODS
Eight instrumented subjects (5 males; 3 females) were exposed in pairs for 135 min to four
randomly assigned conditions inside a liferaft. In the first series of conditions, the floor of the
liferaft was uninflated (~0.2 cm thick) and the subjects were either dry (Udry) or wet (Uwet).
In the second series of conditions, the floor of the liferaft was inflated (~15 cm thick) and the
subjects were again either dry (Idry) or wet (Iwet). The four conditions were repeated with an
additional 4 subjects in the liferaft for a total of 6 occupants (Udry6; Uwet6; Idry6; Iwet6) to
examine the effect of multiple occupants on the thermal responses of the two primary
subjects. During the exposures, the subjects wore a one-piece cotton coverall, an inflated
SOLAS approved personal flotation device, and neoprene gloves and boots to minimize the
risk of non-freezing cold injuries to the extremities. In the wet conditions, the clothing of the
subjects was fully wetted before entering the liferaft. The ambient conditions during the trials
were representative of mild sea conditions: 16°C water temperature, 19°C air temperature, 60
% relative humidity, and 5 m/s wind speed. To simulate for the leeway effect and sea state
(increased convection), the liferaft travelled over water at a speed of 0.5 m/s for the duration
of the trials. The liferaft tested was a 16-person raft with a closed canopy (3.3 m
circumference, 1.7 m height). A constant flow of fresh air (2 occupants conditions: 19 L/sec;
6 occupants conditions: 38 L/sec) was added to the raft to keep the CO2 concentration at an
acceptable level during the trials (