Lifejackets are usually used by professional seafarers whereas flotation devices have their domain in recreational use. Both groups of individual rescue devices share many of the same features. The key issues of lifejacket designs are (2,3):
- Requirement for self-righting.
- Integrated spray-hood.
- Compatibility with immersion suits.
- Easy donning for optimal user compliance.
Continuous education on the use of the systems is mandatory for best performance in a real sea-survival scenario.
For any life-jacket or flotation device it is most important that it brings the person back to the surface immediately in order to prevent drowning. Back on surface it must ensure a high freeboard with a maximum of oro-nasal clearance for prevention of surface-drowning in cold water as well as to support the survivor if they are impaired by bad physical conditions. A stable supine position must be ensured for these same reasons.
Over the last 25 years improvements in fabrics, insulating material, waterproof zippers and introduction of the spray-hood have led to much more reliable suit design. This was initiated by the IMO immersion suit standards, the offshore oil industry demands for better quality and international military-commercial developments, such as submarine escape and immersion suits with surface survival times of 24 hours under the worst environmental conditions. A common problem is the incompatibility between clothes or survival suits and lifejackets. The core problem is the inability of life jackets to self right immersed persons wearing high buoyancy suits and the best solution is an integrated immersion suit that includes the life jacket as part of the system (2).
Importance of Dry Suits
As little as half a litre of leakage of water into the suit (or sweat and urine) reduces the insulation value by one third.
The long term effects of hypothermia can be prevented only by a “really dry” dry suit.
The key issues of good dry suit design are (2,4):
- Reliable neck and wrist seals by continuous rubber collar.
- Easy entry, single-handled with perfect sealing zip closure.
- Fitting neoprene gloves and sized rubber made Wellington boots.