Lifeboat Habitability and Effects on Human Subjects

Abstract

Lifeboats are the most used marine evacuation craft in both the shipping and offshore industries. The International Maritime Organization (IMO) Lifesaving Appliances (LSA) code does not have criteria for the manoeuvring performance of lifeboats nor for their habitability and effects on human subjects. During standard seakeeping exercises conducted with a SOLAS approved 20-person lifeboat in Conception Bay, NL two NRC employees (coxswain and assistant) wearing certified immersion suit systems had their skin temperature, deep body temperature, and heart rate measured while performing their assigned duties. During the morning of July 24th, 2009, the outside air temperature was 14°C and the water temperature was approximately 7.6°C, with little to no cloud cover. While piloting the lifeboat with the hatches closed, the interior temperature of the lifeboat rose from 19.4°C to 28.5°C over the course of approximately two hours. With the immersion suits fully zipped, the coxswain experienced an increase in mean skin temperature of 3.4°C, while the assistant’s rose by 2.7°C. The coxswain’s mean body temperature rose by 0.74°C, and the assistant’s by 1.0°C. After the two-hour time period, both the coxswain and assistant’s clothing were heavily soaked with sweat, and both reported moderate levels of thermal discomfort due to the heat. In the afternoon of the same day, with little to no cloud cover, the outside air and water temperatures registered 15°C and 8.78°C, respectively. For the afternoon trials, the lifeboat hatches were left open, and the immersion suits were unzipped. Over a two-hour period, the interior temperature of the lifeboat rose by only 0.2°C, the coxswain’s mean skin temperature rose by 0.5°C, and the assistant’s by 0.5°C. After the two hour afternoon session was completed, both the coxswain and the assistant reported little to no thermal discomfort with the interior temperature of the lifeboat. Based on these preliminary observations, prolonged occupancy of a sealed lifeboat with a high level of clothing insulation may lead to increased thermal stress on the evacuees.