Chapter 2 : How can we protect from the four physilogical stages of cold water immersion


For the reader who has skipped Chapter 1 and moved straight into this chapter, the four physiological stages are: cold shock, swimming failure, hypothermia and post rescue collapse. The basic principle of protection is to prevent contact of the cold water with the skin. The areas of the body that are particularly important with regard to cooling on immersion in water are, for different reasons, the head, back of torso and limbs. The head has only a weak vasoconstrictor response, thus blood continues to perfuse this area even in the cold. Consequently, a lot of heat can be lost from the head and when unprotected it can be a major route of heat loss. Head immersion can significantly accelerate the rate of fall of deep body temperature and the onset of hypothermia (Froese and Burton (1957), (Reference 46). The combination of reduced blood flow to the extremities and the horizontal flotation angle adopted in the water when most immersion suits are worn, results in the greatest percentage of heat loss occurring through the back of the torso by conduction. One reason for this is that the hydrostatic compression of the suit can reduce insulation in this area (Tipton and Balmi, 1996) (Reference 159). Due to peripheral vasoconstriction, relatively little heat is lost from the core of the body via the limbs when the body is cooled. However, one consequence of the reduction in blood flow to the extremities is that local tissue temperature in these areas falls and neuromuscular function can be quickly impaired. Survival can then be compromised by the inability to use the hands for essential survival actions such as boarding life rafts, deploying life jackets or firing flares (Tipton and Vincent, 1988) (Reference 151).

For the layman who may not appreciate the severity of being immersed in icy water, the sinking of the Empress of Ireland in 1914 in under 14 minutes off Rimouski in the Gulf of St. Laurence paints a dreadful picture.

The ship sank, as she did so, a great and terrible cry arose from 700 throats. Where the ship had been was a struggling mass of men, women and children "as thick as bees" Those who had lifejackets found themselves dragged down by those who had not…

The scenes below decks (of the Storstad that had collided with the Empress of Ireland, but remained afloat to conduct the rescue), defied description, 1012 perished.

Drawn by a desperate search for warmth, hundreds of survivors crowded into the engine and boiler rooms. Some of them leaned against the cylinders until their flesh blistered. Women, shuddering with cold, tried to dry their scraps of nightdresses. Many of them were so frozen that they could not even remove what little clothing they were wearing. Mrs Andersen had to undress them and put on their numbed bodies whatever garments she could find. Then the women were packed into the Norwegian seamen’s narrow bunks two by two, head to toe like herrings in a can, to warm each other back to life. (Croall, 1978) (Reference 38)

The immediate solution that springs to mind is that practically speaking, it should be possible to enclose the body of a person up to the neck in some form of water tight or semi water tight garment or enclosure to prevent the cold responses. This is precisely the approach that has been taken to date. Indeed, the British Merchant Advisory Committee had known this since 1922, yet had done little about it (Reference 112).

The personal garment has under gone a whole series of name changes over the years: anti-exposure suit, immersion suit, marine abandonment suit, poopy suit, and survival suit. In this report it will always be referred to as an immersion suit, except where it has been used by authors to describe either a specific physiological experiment or marine accident report in their own literature.

At opposite ends of the world, two accidents occurred within a day of each other only recently. They emphasize that a personal immersion suit is just as necessary today in the 21st century as when humans took to the water thousands of years ago. As in Chapter 1, other accidents that occurred more recently will be discussed later to emphasize specific problems.

10 Reported Dead in Ferry Sinking (Oslo) (Halifax Chronicle Herald, November 27, 1999)

Ten people died and another 11 were missing and feared drowned after an ultra-modern Norwegian ferry sank in chilly, rough seas off western Norway on Friday.

Hopes of finding any of the missing alive were fading hours after the sleek Sleipner catamaran, with 88 people aboard, went down in the North Sea after hitting rocks near Haugesund in stormy weather after nightfall.

Ferry Founders off China (Halifax Chronicle Herald, November 26, 1999)

On Thursday, more than 24 hours after the ship’s first distress call, just 36 people had been rescued from the cold seas after sinking of the 9000 tonne Dashun ferry which carried 312 passengers and crew.

A similar catastrophe to either of these could easily occur to Canadian ferries, for instance on the run between Sydney, Nova Scotia and Newfoundland, or, Yarmouth, Nova Scotia and Bar Harbor, Maine. Currently with no protection, similar death rates can be predicted. The crew and passengers in the William Carson had a very close call in June 1977. The ferry en route to Goose Bay was holed by ice and sank very rapidly off St. Anthony’s, Newfoundland. Miraculously, all 128 ship’s company and passengers made an orderly and safe escape into the lifeboats in the dark (Reference 145).

Physiological Studies Conducted in Europe and North America 1939 - 1945

During the Second World War, none of the Navies on the Allied or Axis side wore immersion suits. Therefore, it is not surprising that the Talbot Report (1946) (Reference 147) and McCance et al’s report (1956) (Reference 108) showed that between 30- 40,000 sailors had simply drowned while escaping from the ship, i.e. during the survival phase. During the War, T.E. Metcalfe had invented a simple exposure suit for merchant sailors. By 1944, over 300,000 had been produced (Reference 22). Too often the suits went missing when required because there were often used for purposes for which they were never intended, i.e. painting ship. They were too flimsy for prolonged wear and were only meant to be used once in the liferaft and not during the abandonment into the water. Practically speaking, they probably made very little difference to the overall gloomy survival statistics. Macintosh and Pask (1957) (Reference 107) conducted their then secret pioneering work on the performance of lifejackets, but the fruits of their efforts were not realized in lifejacket improvements until well after hostilities ceased in the 1948 SOLAS standard and the 1963 BSI standard.

As mentioned in Chapter 1 under the post rescue collapse section, the Germans noted the terrible loss of critical personnel in sudden cold water immersion accidents. The sinking of the Bismarck and loss of airmen who bailed out alive and well into the cold North Sea during the Battle of Britain caused their physiologists and aviation medicine physicians to examine the problem. They commenced a large Research and Development program, which in part was the cause for the infamous Dachau experiments (Matthes, 1946) (Reference 109) and (Alexander, 1946) (Reference 4). They were the first to observe the "after drop" or continuation in reduction of body core temperature after being withdrawn from the cold water. They also experimented with survival suits and the Deutsches Textilforschunginstitut in München-Gladbach, ingeniously produced one that provided the insulation using soap bubbles (Alexander, 1946) (Reference 4), which appears to have gone into limited service (Reference 147).

Across the Atlantic during the Second World War, Canada, under the initial leadership of Professor Banting at the RCAF Institute of Aviation Medicine in Toronto was active in the research and development of an immersion suit for the Navy and Airforce. In 1941, Gagge, Burton and Bazett were having trouble explaining to the soldiers, sailors and airmen how much insulation to add or subtract to their clothing depending on the outside air temperature, their level of exercise / work and whether they were resting or not. They conceived the unit of Clo as a measure of clothing insulation, which could be used by heating engineers, physicians and physiologists (Gagge, et al, 1941) (Reference 47). It is defined as 0.155° C .m2.W-1, and is the insulation required to maintain comfort when a resting human is in an environment of 21° C , 50% relative humidity and with an air movement of 0.1 metres second-1. The European equivalent to a Clo used for sleeping bags and duvets insulation is the tog, which is 0.645 Clo . Clo value and its measurement will be discussed later in the report.

1 Clo = 0.155° C .m2.W-1

1 Tog = 0.645 Clo

0.1° C .m2.W-1.

Probably the largest equipment trial ever to be conducted was carried out on behalf of the Royal Navy in 1943 by the Royal Canadian Navy in Halifax, Nova Scotia. Surgeon Captain Best from the RCN Medical Research Unit (who in collaboration with Banting had discovered insulin in 1921) managed the huge project and the US Navy provided additional ships and American personnel as subjects (Reference 24). All of the often conflicting requirements that face designers of immersion suits today, and difficulties in providing them, were identified, including lightness, simplicity, wrist and neck seals, zips, closure and drawstrings, ease of donning, addition of gloves or not and flammability were noted (Hiscock, 1980) (Reference 79).

In 1942, Frankenstein’s in the UK had developed a leather immersion suit for the Hurricane pilots protecting the Murmansk convoys who were forced to ditch in near freezing water after launching because there were no aircraft recovery systems. Count Morner in Sweden (Reference 116) also invented a survival suit for merchant seamen during the war, but generally the principle throughout the world was to float survivors in rather than on the water, hence the grim survival statistics. By the end of the War, the Royal Canadian Air Force had developed an immersion suit for their ferry pilots (Figure 15) that went into limited service.

The US Navy was much slower in evaluating the requirement for immersion suits, because they did not join the war until later, and their operations, particularly against the Japanese were in relatively warm water, whereas the British, Canadian, and German operations were in sea water that rarely rose above 15-16° C , and for many months of the year was below 10° C . Another reason, was that their operational staff was still not convinced of the lethal effect of suddenly immersing humans in cold water. Therefore, funds and staff for R&D were slow in coming; so, they made only slow progress during the war. Important, however was the realization by Spealman (1944) (References 138) and Newburgh (1968) (Reference 119) of the dangers of hypothermia caused by cold water immersion.

All the initial, practical work in the US was done by LCdr. Hiscock in the Emergency Rescue Equipment Section ( ERE ). All the scientific work was done under the leadership of Dr. Newburgh at the NMRI in Bethesda. At the ERE liaison meeting in June 1943, the minutes reflected the fact that "lifesaving suits" had proved to be dangerous. The committee recommended that they be replaced by the "protective exposure suit" developed for the US Coast Guard by the B.F. Goodrich Company. This, according to Hiscock was the first reference by the committee to exposure suits for naval and merchant seamen. At the ERE conference in August 1943, the recommendations were that the immediate requirements of the suit were:

  1. As light as possible, for the least amount of bulk
  2. As simple as possible, without watertight zippers
  3. The hands must be free, with adequate wrist closures
  4. Could be used with a separate flotation jacket underneath; and could be stowed on the back of a lifevest or jacket (Reference 79)

Yet, typically after the war, all this research was shelved and no further work was done to protect the sailor or merchant seamen.

The ERE section was transferred to the Air Sea Rescue organization in 1944. Although an improved kapok life jacket was introduced into the Coastguard as a result of their work (Reference 3), it would appear in the US that immersion suits were commercially produced in very few numbers for the remainder of the war.

Physiological Studies Conducted in Europe and North America 1945 – 1970

The massive loss of life at sea during the War triggered several countries into investigating the problem. This section describes many of the different experiments that were conducted to explore the problems. It will illustrate:

  1. the range of investigations
  2. different concepts and design of suits
  3. subjects tended to be of white European or North American stock
  4. divers were often used as subjects, and they tended to already be cold acclimatized
  5. that experiments were done in calm or calm stirred water
  6. the lack of women as experimental subjects
  7. the lack of very large numbers of male subjects in each experiment
  8. that all the subjects were basically young, fit and healthy
  9. the wide range of water temperatures examined
  10. initial difficulty with procuring reliable, waterproof zips
  11. recurrent difficulty with keeping the suits waterproof
  12. quality control when prototype suits were massed produced
  13. little standardized experimental protocols, thus making it very difficult to make direct comparisons from one investigator’s experiment to another one.

It was the Air Forces of the world that led the way. It was not until 1983 that the commercial marine industry and international regulators adopted an immersion suit standard through the International Maritime Organization. In all the experiments the requirements for an immersion suit were:

  1. It should be lightweight and easy to don
  2. It should be waterproof, but the fabric must be suitable for constant wear (i.e. breathable)
  3. It should be compatible with other equipment such as lifejackets.
  4. It should not hinder the ability to conduct essential survival actions when in the water, and it should be possible to swim in it.
  5. It should be ergonomically designed to fit a wide range of the population.

In fact, the majority of experiments were done in a back to front fashion. The suits were tested on various humans, then the conclusion was made that a human could predictably survive a certain time in that water temperature with that specific type of suit (Figure 7).

As we enter the 21st Century and more and more reports are stored in databases or websites, many of the earlier reports have either been forgotten or thrown out to make more space, or because they were more than 25 years old. Already some of this early work has been lost forever. (McCance’s depositions, Lee’s lifejacket work). The author makes no excuse for the length of the next two sections. This holds the key to the basic research and without this being documented in its entirety, new scientists will find it impossible to understand how the research and development was conducted.

Figure 7: Early Post-war immersion suit trials by the US Coast Guard (Don’t these suits still look familiar!)


In 1946, Newburgh, Spealman and Van Dilla identified the physical problems of protecting the hands in cold water (References 119 and 139) but as mentioned above, work did not accelerate in the US until after the start of the Korean War.

In the meantime, in the UK , the Medical Research Council funded a large series of experiments that were conducted under the auspices of the Royal Navy Personnel Research Committee. This resulted in a thorough analysis of the problem in many laboratories and culminated in a whole series of field trials. From this work the once-only ship abandonment suit, the new RFD inflatable pattern No. 5580 life jacket and the first submarine escape suits were developed for the Royal Navy. In parallel with this, the Royal Air Force developed the Mk 1 through Mk 8 aircrew constant wear immersion suit. The first six Mks were made from neoprene nylon, and from 1951, the Mk 7 onwards was made from ventile fabric, invented by the Shirley Institute just post war. The novelty of the fabric was that it was woven from Egyptian cotton in such a way that it would allow body moisture (i.e. water vapour) to pass through the interstices of the fabric, yet when immersed, the cotton fibres would swell to produce a waterproof garment. In practice, it was found that suits had to be made from two layers of fabric to prevent the hydrostatic force of the water pushing its way through a single layer of fabric before the fabric had time to swell (Reference 172). Other disappointments were that it was very expensive to manufacture, expensive and labour intensive to construct the suits, and the fibres would not swell effectively when exposed to body sweat or greases. After the Mk 8 suits, all subsequent ones were manufactured as one-piece suits.

Across the Atlantic in the US , Bradner in 1951 used neoprene foam for immersion suits for the first time (Reference 19). In 1952, the US Navy formally recognized that their life saving equipment during World War ll had been inadequate (Reference 167). They commenced a large R&D project over the next 15 years to find a survival suit for their sailors and a constant wear immersion suit for their naval aviators flying over cold water. The principal work was led by Newburgh who reported his findings in his textbook, Physiology of Heat Regulation and the Science of Clothing (Reference 119). A major trial by the USN in 1955 of eight versions of three immersion suits did not result in the production of a good suit (Reference 166). The USAF also noted losses in cold water off Korea and their work was led by Hall and his colleagues at Wright Patterson AFB. They used the thermal manikin extensively with the US Navy and the US Army Research Institute of Environmental Medicine. Typical manikin results by Bogart et al (Reference 25) in 1966 are listed in Table 1.

Table 1: Immersed Clo values for ten suits tested at USARIEM in 1966

USARIEMin 1966">

Ensemble Immersed Clo w/o head
Unisuit with Arctic Explorer Undergarment 1.34
Viking with Grey Foam Undergarment 0.87
O’Neill Supersuit with Blue Fluff Undergarment 1.27
White Stag with Neoprene Shorty 1.11
Unisuit with 2 sets Arctic Explorer Undergarments 1.55
Viking with O’Neill Blue Fluff Undergarment 0.73
Unisuit with Foam Undergarment (Viking)
O’Neill Supersuit with Navy Waffle
Unisuit with Spacer Garment 1.13
O’Neill Supersuit with Spacer Garment 1.07

The most important work was reported by: Hall et al (1954, 1956, 1958) (References 61, 62 and 63), Beckman et al (1966) (Reference 19), Hall & Polte (1960) (Reference 64), and Goldman et al (1966) (Reference 58). There were four practical findings that came out of their work for the designers of immersion suits:

  1. suits lost 57% of their insulation through hydrostatic squeeze when the human was immersed to the neck
  2. a leakage of as little as a litre of water into the suit reduced the insulation by 22%
  3. maximal body insulation, which is approximately 4 Clo per inch thickness of fabric does not significantly prevent the hands from cooling down
  4. it was possible to categorize of all the different survival equipment by their Clo or insulation value and prescribe different Clo values for different operations

About 1960, the US Naval aviators had discarded their Mk 4 dry suit consisting of a rubber coated outer shell, a quilted insulation liner and elastic wrist and neck seals for a Mk 5 suit. This had a split zippered neck seal and an air ventilation system for cooling. This was followed in the late 1960s by a CWU-9P wet suit system (Reference 103).

Of all the occupations that require protection particularly from cold shock, swimming failure and hypothermia, professional fisherman are most at risk. Fishing garments have not changed for many years (Figure 8). In 1966 both Schilling (Reference 135) and Newhouse (Reference 120) observed chronic fatigue, contact dermatitis and a high mortality due to drowning from being washed overboard in high seas. Between 1959 and 1963, deaths in the British trawling industry averaged one person every six weeks. In 1970, a combined team of the Trade Union Congress, the Medical Research Council, the RAF Institute of Aviation Medicine and the Army Personnel Research Establishment proposed a new light, warm, wet proof, well fitting garment that was positively buoyant and reasonably priced (Newhouse, 1970) (Reference 121).

Figure 8: A sketch made by M.J. Burns of typical rig worn by fishermen and the US Lifesaving Service in the 1880s. (Photo courtesy of US Coast Guard)


There are a number of other important scientific papers related to this work from the UK and Canada on immersion suits and life jackets that were published during this period. Allen in Toronto unsuccessfully tried to find a replacement for the RCAF anti-ditching suit (Reference 10); Baskerville reviewed the status of protective clothing for the RN aviators (Reference 18); Crockford commenced his work on finding replacement protective clothing for the fisherman (Reference 39); Glaser and McCance reported on the first Arctic trial of RN protective clothing (Reference 52); MacIntosh and Pask were finally allowed to publish their previously secret pioneering lifejacket work form the Second World War (Reference 107); and Pugh et al published their work on the RN submarine escape suit (Reference 131).

Major publications which should be essential reading for all involved in the design and development of immersion suits and survival training published as a result of this twenty five years of research include:

  • Man in a Cold Environment (Burton & Edholm, 1955) (Reference 31)
  • Survival in Cold Water (Keatinge, 1969) (Reference 92)
  • Safety and Survival at Sea (Lee and Lee, 1989) (Reference 98)
  • The Hazards to Men in Ships Lost at Sea (McCance, 1956) (Reference 108)
  • Physiology of Heat Regulation and Science of Clothing (Newburgh, 1968) (Reference 119)
  • Survival at Sea (Smith, 1976) (Reference 136)

Practical Immersion Suit Trials 1970 – 1980

By the beginning of the 1970s, the general opinion was that hypothermia was the principal threat from sudden cold water immersion and that the best protection was a dry suit. However, manufacturers found it difficult to mass produce immersion suits for constant wear that were affordable. Good quality waterproof zips were expensive and cheaper alternatives did not work, quality control on the production of the suits was poor, so even brand new suits leaked. The only alternative to the neoprene or chloroprene coated fabrics was ventile fabric and as previously mentioned, this was expensive to manufacture and assemble into suits. With the difficulty of making a truly dry suit and facing the consequences of it being too hot and uncomfortable for constant wear, thoughts were given to producing wet suits.

It is important for the reader to have a definition of what is a dry suit and what is a wet suit.

  1. A dry suit is designed to function by keeping the insulation worn beneath it dry. This is achieved by the use of water tight seals, zips and impermeable material. A dry suit may or may not have insulation (insulated and uninsulated suits).
  2. A wet suit should be a close fitting garment which functions by trapping a layer of water next to the skin. This allows only a small volume of water to enter the skin / suit interface. This is warmed and does not have a significant effect on the inherent insulation provided by the suit.

In this ten year period, a whole series of immersion suits experiments took place in Australia, Canada, Finland, the Netherlands, Norway, Sweden, the UK and the US – basically countries where marine operators were working in cold water. Unfortunately, there has never been a true international joint commercial-military project to develop a suit, much of the work has been disjointed as can be seen in this and subsequent paragraphs. Riegel evaluated a whole series of suits over the winter of 1973 for the US Coast Guard. His protocol in Table 2 is an excellent model for all researchers to use (Reference 132). Crockford continued to improve the UK fishermen’s work dress (Reference 40); Millward evaluated several suits for the UK fishing protection officers (Reference 114); Hampton evaluated the latest immersion suits for helicopter pilots flying for the UK offshore oil industry (Reference 66) and Werenkskiold evaluated the newer immersion suits at the Norwegian Ship Institute (Reference 171). Goldman continued to work with humans and the manikin on survival problems for the USAF , Army and Navy (Reference 59); Johansson evaluated a very large number of 20 immersion suits for the US Naval aviators (Reference 86). Hall predicted survival times wearing immersion suits in a life raft (Reference 65) and across the other side of the world, White conducted immersion suit trials to find a replacement suits for the Australian military pilots flying over the Bass Straights to Tasmania (Reference 173).

Table 2: Summary of Suit Evaluation Data

  Imperial QD-1 Plus Preserver Empress Deck Suit
Tolerance Time, hr 14 2.2 2.4 5.8
Face-Up Float Stability Yes Yes Yes Yes
Self-Righting Capability No Yes No No
Freeboard (inches) 3.5 5.5 3.5 3.6
Donning Time, min. 0.89 1.3 0.6 0.9
Color Orange or Yellow Yes Yes Yes Yes
Retroreflective No No No Yes
Stowage Vol. , ft 3 1 0.8 0.1 1
Maintenance Freq. , yr 5 5 5 5
Cost $75 $120 $125 $100
Walk Speed, ft/min 333 370 357 333
Climb Ladder, ft/min 77 91 100 91
Can Emerge from Water Yes Yes Yes Yes

The offshore oil industry was also keen to procure the best ship abandonment immersion suits and helicopter crew and passengers suits. In 1978, Hayward et al from the University of Victoria, British Columbia, conducted the largest immersion suit human physiology trial so far performed in Canada (Reference 72). They evaluated 23 different military and civilian suits. The suits fell into three distinct categories: dry with closed cell foam - dry without foam, and wet with closed cell foam. All twenty subjects were immersed for 2-3 hours in ocean water at 11.8° C off Banfield, B.C. These suits represented the current state of the art twenty-four years ago, and are listed in Table 3.

Table 3: Evaluation of twenty-three military and civilian immersion suits.

Design-Concept Suit Code (Series and number) Suit name Country of manufacture
Dry, without foam ( D ) D 1 Beaufort Quick-donning England
  D 2 Jeltek "Seacheater" England
  D 3 CWU-16/P US
  D 4 Beaufort Ventile Mk 10 England
  D 5 Hansen Ventile Denmark
  D 6 ILC Dover (AE1) US
  D 7 Multifabs England
Dry, with foam ( DF ) DF 1 Bayley US
  DF 2 Fitz-Wright Canada
  DF 3 Imperial US
  DF 4 SIDEP "Seastep" France
  DF 5 Multifabs (foam model) England
  DF 6 Helly-Hansen (D600-0) Norway
Wet, with foam ( WF ) WF 1 Imperial (model H) US
  WF 2 Imperial (flight) US
  WF 3 Harvey’s US
  WF 4 CWU-33/P (long-sleeve) US
  WF 5 CWU-33/P (short-sleeve) US
  WF 6 Mustang (model 175) Canada
  WF 7 Wendyco "Norwester" England
  WF 8 Mustang "UVic Thermofloat" Canada
  WF 9 WF 8 plus "Sea-seat" Canada
  WF 10 Fitz-Wright diver’s Canada


C 1 No survival suit  

Not surprisingly, the human cooling rates in the suits fell into three categories too, the dry insulated suits having the slowest rate (0.31° C hr -1) and the dry uninsulated suits having the highest rate (1.07° C hr -1). From this work, Hayward et al. were able to compile a very useful guide as to the number of hours to reach three levels of hypothermia (27° C , 30° C , 33° C ) when immersed in 8 - 11° C water.

Operational trials were conducted in realistic conditions to assess how long humans could survive in various wet or dry suits. The conclusions from each experiment revealed similar findings. In the early days, the quality control on the manufacture of suits was poor: many brand new suits leaked so badly that the subjects had to be physically lifted out of the water after only a short immersion; and some groups of people even refused to wear them. The quality and reliability of the early zips was poor and ventile fabric was not the success that everyone had hoped. It also became apparent, that to survive in North Atlantic type water, which rarely warmed up above 16° C and was often in the single digits, a dry suit was essential. Both manikin and human testing showed that even a small leak had a profound effect on reducing Clo values as did the effect of hydrostatic squeeze. Moreover, it was very difficult to keep the hands warm even with the maximum insulation worn on the body. Up until this time there was still no internationally recognized immersion suit standard.

There was also a much bigger customer demanding better suits and that was the offshore oil industry. Their sponsorship and funding were the key to the improvement in immersion suits over the next 20 years.

1980 – 2002: The Offshore Oil Industry Requires Immersion Suits

By 1980, a whole series of second generation suits were being manufactured and tested. These were principally being used by the now well developed offshore oil industry for both helicopter ditching and ship/rig abandonment. After the Alexander Kielland accident in 1980 and the sinking of the MS Malmi, the Norwegians and Finns evaluated a number of suits with now familiar names such as: Aqua Suit, Bayley, Beaufort, Fitz-Wright, Helly-Hansen, Imperial, Lifeguard, Liukko, Manu, Multifabs, Nokia, Nord 15 and Shipsafe (Reference 93).

Generally, there was still dissatisfaction with the suits and only too familiar comments:

  • Flotation position was not satisfactory (too little freeboard)
  • Small people nearly get lost in the suit after a five metre jump into the water
  • Leakage on glove seal with suit
  • One size suit does not fit everyone
  • All zippers need regular maintenance
  • Very difficult to swim in the suit
  • Leakage into the suit, which in some cases caused great difficulty in boarding liferaft
  • Poor durability of fabric
  • Requirement for good maintenance

As described in Chapter 1, in 1981, Golden and Hervey published their classic work on the physiology of sudden cold water immersion (Reference 56). In 1983, the next major achievement was the ratification of the International Maritime Organization, SOLAS standard for insulated and uninsulated suits (Reference 85).

1986 was a prolific year for reports on survival suits, principally because the International Ergonomics Society held a conference in Helsinki on the specific topic of survival at sea and immersion suits. Hayes (Reference 68) from the RAF Institute of Aviation Medicine, provided a very clear and precise performance specification for an immersion suit at the meeting. The purpose of immersion protection clothing is to:

  • Minimize the occurrence of cold shock
  • Prevent hypothermia and non freezing cold injuries
  • Reduce the likelihood of post rescue collapse
  • In conjunction with personal flotation devices prevent drowning from wind and wave splash as well as from facial immersion

Avery and Light from RGIT , Aberdeen (Reference 13) discussed the problems of leak testing and demonstrated that "good" suits could leak between 145 and 1398 mls of water. Lotens and Havenith from TNO in the Netherlands (Reference 104), examined the ventilation of garments in an effort to improve the comfort of the dry suit. Pasche and Ilmarinen from the Institute of Occupational Health in Helsinki (Reference 129) reviewed the new temperature parameters introduced by the 1984 IMO committee and commented that from a safety point of view, more attention should be paid to skin temperature to prevent non-freezing cold injury; and from Canada, Mekjavik and Gaul from the Simon Fraser University, British Columbia (Reference 111) examined the heat stress produced by a typical immersion suit worn by pilots flying offshore and Sullivan and Mekjavik (Reference 144) examined the ventilation indices of the suits to improve comfort.

The remaining work presented at the conference in 1986 all came from the US. Steinmann et al from the US Coast Guard, (Reference 140) examined the effect of wave motion on the insulation properties of eight different suits. This was further amplified in a paper in the Aerospace Medical Journal (Reference 141). The water temperature was 11° C and eight volunteer Coast Guard crew were exposed to 4-6 foot swells with occasional four foot breaking waves and 2-3 foot wind waves. The dry suits performed better than the wet suits and the tighter fitting suits performed better than the loose fitting suits. They further concluded that survivors in rough seas may have a significantly greater risk of immersion hypothermia than previously assumed based on survival time projections from calm water studies.

Riley (Reference 133) also from the Coast Guard commented on the idiosyncrasies of the introduction of the new IMO standard. The fact was that an insulated immersion suit could be substituted for a lifejacket if the suit met all the performance standards of the lifejacket. He pointed out that the current buoyant immersion suits will not turn an unconscious person face up in the water. Kaufmann and Dejinika from the Naval Air Development Centre (Reference 88) reported on the successful use of Gortex immersion suits by 14 subjects aged 21 – 40 years in 7.2° C water.

In the first five years of this period, several repeat experiments using newer fabrics such as Gortex and Thinsulate and new, waterproof zips were carried out. The findings reconfirmed the requirement for a dry suit, but the suit design essentially remained the same and there has only been a small gain in thermal performance, principally due to better overall waterproofing of the suits.

Allan et al. (References 8 and 9) re-visited the possibility of providing a wet suit for helicopter passengers, the object being to reduce the thermal discomfort of a constant wear suit. However, the shuttle jacket introduced into service by Shell was later withdrawn when Tipton et al (1989) (Reference 152) reported that it did not protect the passenger from the initial responses of immersion in cold water, i.e. cold shock.

As human testing became more expensive and human ethics committees less amenable to using humans simply to test suits to a specific standard, there was an increase in the use of thermal manikins to do this job. As a result of the Ocean Ranger accident in 1982 off the Grand Banks of Newfoundland, Canada introduced specific survival suit standards for ship abandonment suits ( CGSB 1999) (Reference 34) and helicopter passenger suits ( CGSB 1999) (Reference 33) in which the thermal test could be conducted with a manikin.

By now, it was being noted that the equipment in service both for the military and commercial operations had performed "surprisingly poorly" during real accidents. There are still about 140,000 open water deaths reported each year. How could this be when there is such a range of tests and regulations to theoretically prevent this? The answer is that many of the tests are innocuous and not realistic. The tests must either re-create the tasks that may have to be undertaken and / or the environmental conditions which may exist during the accident, or enable prediction of the decrement that will be seen in more adverse conditions. In 1995, Tipton (Reference 158) demonstrated this very clearly with a group of twelve subjects who undertook two immersions wearing identical clothing in two tests: Test A and B. However, in test B, simulated wind (6 knots), waves (15 cms) and rain (36 L / hr ) were introduced as well as a 15 second period of initial submersion. The estimated survival time was reduced from 6.8 hours in Test A to 4.8 hours in Test B (Figure 9).

Figure 9: Estimated survival time with and without simulated mild weather conditions.


(Courtesy Journal of the R.N Medical Services)

The reader is directed to a number of scientific papers relevant to this period. Light et al (1980) (Reference 101) commenced a whole series of immersion studies at RGIT in Aberdeen for the offshore oil industry. Hampton from Leeds (1981) (Reference 65) reported more extensive tests on immersion suits for the offshore oil industry. Baker continued work on improving the RN submarine escape suit (1987 and 1988) (References 14 and 15). Hermann from the Institute of Occupational Medicine in Hamburg (1988) (Reference 75) cautioned the operators about the incompatibility of survival suits and lifejackets. After Allen (1964) (Reference 10) failed to find a good replacement immersion suit for the Canadian Airforce, Hynes et al from Defence and Civil Institute of Environmental medicine ( DCIEM ) (1985) (Reference 82) tested a whole series of new, improved garments. A new suit was finally chosen in 1989 by Sturgeon (Reference 143).

Ilmarinen et al (1981 and 1984) (References 83 and 84) tested a whole series of ship abandonment and helicopter passenger suits for the Finnish Board of Navigation and the offshore oil industry. Kaufman et al from the US Navy (1984) (Reference 87) reported data on the new Gortex material and Thinsulate liners. In Norway, Langhaug et al (1982) (Reference 93) continued work on evaluation of immersion suits and in Sweden, Larsson et al (1991) (Reference 94) suggested modifications to the RN Mk 8 submarine immersion suit. Pasche et al (1982 and 1984) (References 127 and 128) conducted a whole series of experiments on immersion suits at Nutec, Bergen, Norway and reported on the profound effect that leakage made on the insulation value. Romet et al from DCIEM , Toronto (1991) (Reference 134) compared the immersed Clo value of immersion suits measured on humans and on the CORD manikin.

Reviewing the practical immersion suit testing that has taken place since 1945, a general observation is that considerable expense in cost of duplication of technical equipment and materials has occurred over the last 45 years. Added to this, inter-service, inter-academia and international rivalry has slowed down the acquisition of knowledge of cold water physiology. An international military-commercial coordinated effort would have likely made more progress for less cost in less time, and saved stoical subjects some considerable discomfort over the years.

There are subtle reasons why progress was slow at the IMO working group. The first was that members chosen to attend were often not the most knowledgeable in cold water physiology and able to make the correct decisions; and many Nations arrived with a pre-conceived agenda driven by their national industry. As a result, many compromises had to be made. The only practical decision that was made was that a body core temperature of 35° C represented a case of hypothermia, therefore the insulation of the immersion suit should prevent a normothermic test subject from cooling more than 2° C in 2° C water after six hours immersion.

Summary of Chapter 2

This chapter discusses the practical aspects of trying to construct the best immersion suit.

  • It took until the middle of the Second World War for the UK and Germany to realize that there was a problem from sudden cold water immersion. Up until 1945, there were only rudimentary suits in service; however, in 1941, Gagge et al had made the first step by defining the Clo value for clothing insulation.
  • Post war research on survival statistics by the Talbot Committee and McCance et al revealed that the problem was more serious than originally imagined. The US military forces were not finally convinced that there was a problem until after the Korean war.
  • Several critical scientific papers and textbooks are cited as mandatory reading for all students involved in survival at sea and its application to immersion suits such as the effects of leakage, the hydrostatic squeeze on the suit, Clo value and difficulty with protecting the hands.
  • This realization spawned research principally in those maritime countries operating in cold water. The first generation of post war suits did not meet expectations, they were hot, bulky and leaked badly. Much of this was due to poor fabrics, unreliable wrist and neck seals, non-watertight zippers and poor quality control in the manufacturing process.
  • By the mid 1980s, spurred by the IMO immersion suit standards and the offshore oil industry’s demand for better quality, improvement in fabrics, insulating material, waterproof zips and better quality control, there was an improvement in the suit design and reliability. This is also reflected in the number of applied physiological papers cited during this period.
  • Nevertheless, progress would have been more rapid if there had been international military-commercial resolve to investigate the problem sooner.