1 Introduction In considering appropriate thermal protective equipment for use on ships operating in various
climatic conditions, Administrations and ship operators should take into account all of the relevant
risk factors, to include type of ship, type of survival craft, number of persons on board,
environmental conditions in the operational area, and availability of SAR services. The purpose of
these Guidelines is to provide information to assist in the assessment of the impact of environmental
factors, and specifically water temperature on equipment selection. In the context of the medical
threat of hypothermia, the IMO publication .A Pocket Guide to Cold Water Survival. should be
referred.
2 THERMAL PROTECTIVE PERFORMANCE In addition to the performance requirements specified in the International Life-Saving Appliance
(LSA) Code, there are some data available which illustrate the performance of the equipment at
different water temperatures. Thermal protective performance for the various types of equipment at
these temperatures is defined as the time to reach a deep body temperature of 35oC or reduce a deep
body temperature by 2oC, which is the point at which a significant degree of incapacitation is
expected to occur. These data were obtained by a combination of theoretical and experimental
methods. While based upon the best information available, they are provided for comparison
purposes only. Individual results may vary greatly based on sea conditions, body type, etc.
Table 1: Thermal protective performance by type of personal life-saving appliances | Thermal protective means. (Clothing is generally included) | IMO minimum test requirements | Time (hrs) for core temperature drop of 2
°C or to 35 °C when exposed to water of temperature |
| Time (h) | Water temp. (°C) | 0 °C | 5 °C | 10 °C | 20 °C |
| Lifejacket | - * | - | - | 0.5 h | 0.8 h | 1.7 h |
| Thermal protective (TP) lifejacket | 2 h | 10 | 0.5 h | 0.75 h | 2 h | 4 h |
| Anti-exposure suit | 1 h | 5 | 1.5 h | 2 h | 4 h | 10 h |
| Immersion suit uninsulated | 1 h | 5 | 1.5 h | 2 h | 5 h | > 12 h |
| Immersion suit insulated | 6 h | 2 | 6 h | > 12 h | > 12 h | > 12 h |
The sea areas subject to these temperatures vary greatly throughout the year and do not always
uniformly follow specified latitudes. Table 2 illustrates the approximate variation of water
temperature with latitude during the coldest months of the year in the northern and southern
hemispheres. More exact information on seawater temperature can be found at
www.nodc.noaa.gov/dsdt/oisst/index.html or appropriate local sources.
Table 2: Variation of seawater temperature with latitude | Temperature range (°C) | Geographical sectors (degree latitude) |
| North | South |
| Above 20 | 0-30 | 0-30 |
| 20-10 | 30-50 | 30-45 |
| 10-5 | 50-60 | 45-50 |
| Below 5* | 60-70 | 50-60 |