Thermal protective aid

Chris Bolton, who always carries one in his buoyancy aid, commented on the Uk Rivers Guide Forum, the technique for getting oneself inside a polythene survival bag. The bag should be open and held in the leeward, letting the air blew it open. Pulling the rim over the head, the knees should be raised, and bunching the rim into a large fold under the feet, let them slide into the bag. Inside the flooded bag, a swimmer can rest with the upper torso and the head out of the water, protected from spray and splash if the bag is held close leaving 20 minutes of breathing air inside, and by looking like an orange buoy, attaining a higher visibility than simply laying submerged afloat.

The principal advantage of course, is the reduction on heat exchange with the water through forced convection: As long as the water inside the bag, however cold, is not replaced by cooler molecules, it should warm and gain a lower temperature gradient with the skin. The bare lack of relative movement of the fluid reinforces this process.

The best known use of the orange plastic survival bag may be as a shelter. Used in this manner it provides more storm protection and minimizes heat loss to the ground but in this regard, they have been somewhat superseded by the group shelter. A better solution for survival at sea is the thermal protective aids. Known as survival suits, they look very much like a twisted bogey man costume. They were designed for hypothermia protection during prolonged exposure in life rafts or lifeboats, and often have hoods and sleeves, taped seams, a zippered entrance, and reflective tape stripes. Made of waterproof, reflective polymer coated fabrics, the very low thermal conductivity reduces heat loss in cold, wet conditions.

Survival suits can be used as an emergency tent substitute if a day trip is accidentally prolonged, or to warm up a paddler suffering exposure. I once was given a demonstration of this by a Salzwasser coach who deployed out of a small, folded package an immense survival bag in high-visibility orange. I remember the round hood, wide sleeves, and the Solas tape. To avoid wasting energy in warming soaked clothes, the hypothermic victim should ideally be undressed and rubbed gently. I do not recall having regarded at the time, the explanation as sexy as it now seems, but after all, I am very normal. I remember though, the extensive survival instructions printed in the outside. As anything printed in German, they looked deadly.

Thermal protective aids were produced to comply with the Regulation III/32.3.2 of the Solas Convention 1974 that addresses immersion suits and thermal protective aids, and required every cargo ship to carry 3 immersion suits for each lifeboat on the ship, and in addition, if the ship had totally enclosed lifeboats or was constantly engaged on voyages in warm climates, thermal protective aids for persons on board not provided with immersion suits. However, somewhere, marine stores should be offering new survival bags as discarded shipping supplies as since July 1st 2006, an amendment to Regulation 32.3 adopted by Resolution MSC.152(78) on May 20th 2004 at the 78th session of the Maritime Safety Committee of the Imo came into force, requiring cargo ships to carry immersion suits for every person on board unless the ships have davit-launched life-rafts or life-rafts served by equivalent launching appliances or are constantly engaged on voyages in warm climates.

The term “voyages in warm climates” means voyages within the latitudes of 30º N and 30º S.

Original at: http://onkayaks.squarespace.com/journal/2008/12/29/sunday-december-28th-2008-thermal-protective-aid.html