Courtesy: ISO 12402:2006 personal flotation devices
Life jackets for outfitting large commercial transport ventures in potentially dangerous waters, such as coastal cruises, offshore passages, and overwater air flights, consisting of either a single air chamber or a pair of (twin or double) sealed air chambers constructed of coated nylon (sometimes with a protective outer encasing of heavier, tougher material such as vinyl), joined together, and buckled with a side release buckle. For use aboard ships they may be constructed of foam. Twin air chambers provide for redundancy in the event of one of the air chambers leaking or failing to “fire”, for example if the thin air cell fabric is sliced open by sharp metal fragments during emergency evacuation and egress. Most life jackets for leisure use are of the single air chamber type.
Aircraft devices for crew and passengers are always inflatable since it may be necessary to swim down and away from a ditched or submerged aircraft and inflated or foam filled devices would significantly impede a person from swimming downward in order to escape a vehicle cabin. Upon surfacing, the person then inflates the device, orally or by triggering the gas canister release mechanism. Most commercial passenger life jackets are fitted with a plastic whistle for attracting attention. It has a light which is activated when in contact with water.
Quality life jackets always provide more buoyancy than offered by the buoyancy aids alone. The positioning of the buoyancy on the wearer’s torso is such that a righting moment (rotational force) results that will eventually turn most persons who are floating face down in the water (for example, because they are unconscious) into a face up orientation with their bodies inclined backward, unlike more simply designed common foam buoyancy vests.
Today these air chamber vests are commonly referred to as ‘inflatable life jackets or vests’ and are available not only for commercial applications but also for those engaged in recreational boating, fishing, sailing, kayaking and canoeing. They are available in a variety of styles and are generally more comfortable and less bulky than traditional foam vests.
The air chambers are always located over the breast, across the shoulders and encircle the back of the head. They may be inflated by either self-contained carbon dioxide cartridges activated by pulling a cord, or blow tubes with a one-way valve for inflation by exhalation. Some inflatable life jackets also react with salt or fresh water, which causes them to self-inflate. The latest generation of self-triggering inflation devices responds to water pressure when submerged and incorporates an actuator known as a ‘hydrostatic release’. All automatic life-jackets can be fired manually if required. Regardless of whether manually or automatically triggered, a pin punctures the cartridge/canister and the CO2 gas escapes into the sealed air chamber.