Transport Publication TP 13822 E
- Executive Summary
- Chapter 1: The problem
- Chapter 2: How can we protect from the four physiological stages of cold water immersion
- Chapter 3: Key physical issues in the design and testing of immersion suits
- Chapter 4: Key issues in the construction of the immersion suit
- Chapter 5: Inter-relationship between the immersion suit and the lifejacket
- Chapter 6: Who needs protection and what regulations are required?
- It is quite astonishing that over the centuries, hundreds and thousands of humans have drowned in cold water, and it is only in the last 50 years that anyone has taken this death toll seriously. Death was attributed to drowning from an inability to stay afloat and vague terms, such as exposure. This is because death at sea was, and to some degree still is considered an occupational hazard. Fishermen for instance, who are most at risk, simply considered it as on occupational hazard and fate. Any attempt at protection was to float the person in rather than out of the water.
- It took until the middle of the Second World War for the UK and Germany, and post-Korean war for the US to realize that there was a problem from sudden cold water immersion.
- As a result, internationally over the last half of the 20th century, there has been considerable human experimentation in cold water physiology. The pioneering work was done in the mid- 1940s and 1950s, but by the 1960s, it appears to have been forgotten and needed to be relearned. The advent of the offshore oil industry created a demand for more research to produce better immersion suits. This created a flurry of experimentation in the 1980s and 1990s. A number of these experiments have been cited to give the reader the wide scope of them.
- Although the four stages in which death may occur in the cold water accident were known since the Second World War, stage one (cold shock) and stage two (swimming failure) were considered only of academic interest. As a result, regulators, teaching establishments and survival suit manufacturers all concentrated their efforts on protecting the human from hypothermia. In this regard they have done a very good job.
- Even though there are well established teaching programs, good regulations and much improved life saving equipment, there are still in the order of 140 000 open water deaths each year. What has been overlooked is the significance of the first two stages - cold shock and swimming failure as a cause of death. The severity of the effects of cold shock is directly proportional to the water temperature peaking between 10-15° C .
- The layperson and accident investigators are often surprised that some people do not survive a lengthy immersion. Theoretically they are within the "safe" boundaries of one or more of the survival curves that have been developed to predict death from hypothermia. These people do not die of hypothermia per se. They die from a variety of problems in which moderate hypothermia is enough for them to lose their physical ability and mental determination to keep their backs to the waves. They thus inhale the next wave and die from drowning in spite of wearing a life jacket.
- In regard to immersion suits, Eskimos have used "spring pels" to protect themselves from sudden cold water immersion since they took to the water. Crude suits have been available to mariners since the mid 19th Century. A concentrated effort to produce a practical, commercially available suit did not occur until post 1945. Between the 1950s and the late 1970s, the suits were criticized due to poor design, poor fit, leakage and quality control in the manufacturing process. In the last 20 years, with the introduction of several standards, including the 1983 IMO SOLAS standard, improvement in fabrics, zips and better inspection procedures, the water tightness of the suits has improved, and acceptance has improved.
- Fundamental principles of the immersion suit design and development are discussed, particularly the requirements for a dry suit, the necessity for it to be integrated with the lifejacket, the profound, negative effect of leakage on the immersed Clo insulation value, the difficulty of protecting the hands and the penalties for the use of poor materials and quality control in the manufacturing process.
- Thermal manikin technology for evaluating the thermal protection of an immersion suit moved rapidly forward in the 1980s, but has stagnated basically due to lack of funding. Although there are pros and cons for manikin use, the way ahead is to develop a simple manikin for suit thermal testing against a standard. Humans should only be used for new concepts and major modification to already approved suits. More research is needed to clarify the proportional contribution of torso, head and limbs to the heat equation in order to fine tune the next generation of manikins.
- In regards to who should be protected and what regulations require modification or initiation, there are thirteen professional categories that require either a constant wear suit (Group l), a ship abandonment suit (Group ll), or a passenger immersion suit system (Group lll). Modifications are required to the standards related to the Group l and ll suits, but most important, the Group lll (passengers sailing in water below 15° C ) are currently unprotected. In the next two years, Transport Canada should require the carriage of a Navy style quick don immersion suit, within the next five years, an integrated passenger immersion suit system must be developed.
- In regards to the practical advice regarding the regulations requiring the carriage of liferafts and training of operators of passenger carrying vessels.
- Wherever possible, entry into water below 15° C should be avoided. Direct entry into a life raft should be the objective.
- Transport Canada should use this philosophy in the design, development and implementation of all new legislation in a step wise fashion. All vessels operating in Canadian lakes and rivers at 15° C or below should carry liferafts that can easily be launched and boarded by the entire crew and passengers.
- The only exception to this should be where it is physically or practically impossible to stow a liferaft. Under such conditions the passengers must wear inflatable lifejackets when on board.
- Operating a vessel close to the shore or in groups or the carriage of EPIRB are not reasons for waiving this requirement because death from cold shock will occur within 3-5 minutes, swimming failure in under 30 minutes, and darkness only hampers escape and rescue.
- The Marine Emergency Duties curriculum should be amended to include the two new Canadian videos on cold shock, swimming failure, hypothermia and post-rescue collapse.
- A correctly designed and fitted lifejacket plays a vital role in the effort to protect the human from cold shock. Introduction of legislation and regulations since 1945 have had a dramatic effect on drowning statistics. These are at an all time low in Canada of 1.2 per 100,000 population.
- This does not allow any complacency because work still needs to be done on the nomenclature of flotation devices (lifejacket v. PFD s), improvement in self righting tests, a review of self righting requirements, co-ordination of new standards with the IMO / ISO / CEN standards, and the question of legislation of the wearing of flotation devices on small passenger vessels. More attention should also be paid to how fashion positively or negatively affects the wearing of lifejackets and personal flotation devices.
- If the decision is made to develop new standards for lifejackets (inshore and offshore) and PFD s (generally domestic and recreational) then because there is so much commonality between them, neither must be developed in isolation of each other. Furthermore, it is essential that preferably the committee chairman or senior representative for both standards should both attend each other’s meetings and also international meetings with IMO / ISO / CEN . If this does not happen an incongruous situation may occur where common essential parameters may not be in agreement.
- For those destined to develop the integrated immersion suit system, it must be remembered that:
- getting wet is potentially very dangerous
- a dry system must be provided to achieve protection from the four stages of immersion
- leakage of as little of 1/2 litre of water into the system will reduce insulation by 30%
- the maximum insulation that can be added to a suit to prevent heat loss and still be wearable is 4.5 Clo in air
- protection of the hands in the longer term is problematic, but not essential to survival, providing function is maintained for critical tasks
- testing should be as realistic as possible to avoid disappointment with the function of the final product in the survival situation
A Thermal Immersion Suit Experiment Using the Latest Technology with Humans and the Manikin in the Laboratory and at Sea.
Heat flow discs applied to skin of subject; inner liner donned and heat flow discs applied to this layer; outer shell immersion suit donned and heat flow discs applied to the external surface.
Thermal manikin prepared in exactly the same manner and ready to be loaded into cradle; manikin loaded in cradle and positioned at correct angle.
Manikin and human floating in the NRC Institute of Marine Dynamics wave tank; manikin loaded in cradle and ready to go to sea; manikin and human riding three metre waves in the Atlantic Ocean offshore in 2 ° C water, Halifax, Nova Scotia.