The Swedish Accident Investigation Authority (SHK) has observed how life jackets operate in various conditions, and the importance of maintenance and knowing the advantages and disadvantages of different types of life jackets. The text below is taken directly from the final report by SHK, RS 2016:08 Öring and barge capsizes in the Göta river. The text has been shortened slightly.
2.12.1 Inherently buoyant life jackets
An inherently buoyant life jacket (often called a PDF or personal flotation device) is made of synthetic materials and contains fixed flotation elements. There are different types of inherently buoyant life jackets such as life preservers, all-round life-jackets and working life jackets. Fixed floating elements are made of a material that is lighter than water, usually polyethylene or PVC closed-call foam. All-round life jackets are the most comfortable type and can often be worn under working clothes to give a warming effect. Inherently buoyant life jackets are designed to help the user to remain on their back in the water. These life jackets are thus suitable for non-swimmers and can support unconscious persons. Other inherently buoyant life jackets such as all-round life jackets and working life jackets are intended to keep the user afloat but have no turning effect. Such life jackets thus require that the wearer can swim. An inherently buoyant life jacket is in principle maintenance-free and has no temperature limits.
Life jackets are divided into different types according to their area of use. They are also classified into different international ISO standards. Among other things, the different classes define minimum requirements for a life jacket’s nominal lifting power expressed in Newtons (N). These classes are 50 N, 100 N, 150 N and 275 N and relate to a user’s body weight that is greater than 70 kg and the transferred lifting force in Newtons. An all-round life jacket has a rating of 50 N or more. A life preserving jacket has a rating of 100 N or more. An inflatable life jacket has a rating of 150 N or more.
2.12.1 Inflatable life jackets
It is now common to use inflatable life preserving jackets that are blown up automatically or manually. Some manufacturers recommend a crotch strap, but most inflatable life preserving jackets on the market are approved without such a strap. A crotch strap usually gives a better floating position and in a choppy sea a person can follow the waves better with a crotch strap. Inflatable life preserving jackets should not be worn under working clothes. They are designed to help the user onto their back and keep the nose and mouth above the water. Manufacturers recommend annual inspections of inflatable life preserving jackets, since certain parts of the jackets must be replaced at regular intervals and other parts after they have been used. Inflatable life preserving jackets are also available in a version for professional shipping which are approved by SOLAS. The life preserving jacket must have redundancy in the inflation process, so that it can be inflated by mouth if the cartridge fails. Tests carried out to inflate life preserving jackets at low temperatures (minus 20 degrees) show that the inflation mechanism is triggered at low temperatures, but the carbon dioxide may form ice plugs which slow down inflation and some of the carbon dioxide is unused at very low temperatures, which can also reduce the inflation effect. Some producers state that at temperatures lower than five degrees centigrade, inflation of the life preserving jacket is less effective.
If you use different types of inflatable vests in your occupation, the Transport Agency would like you to contact them if you notice any shortcomings or problems in the functioning of the vests. This applies to both old incidents as well as more recent ones, to give an overall view of the type of problem that arise and their frequency.