Originally Posted by Louise
One type uses a salt tablet which triggers the jacket to inflate when it dissolves. This kind can occasionally go off when you don't want it to, e.g. if the lifejacket gets very wet. Just ask Mr Kennett...
The other 'hammar' type works by water pressure so is not likely to inflate 'accidentally'.
I have had passengers' lifejackets inflate twice. Each was caused by very substantial amounts of water cascading into the boat. Interestingly one was a conventional auto lifejacket, the other was a Hammar -- on neither occasion did my lifejacket inflate as I was hiding behind the console at the time!
I would have no hesitation in chosing the cheaper conventional type over the more expensive Hammar as I don't think that the advantages are particularly significant.
The cheaper type do fire occasionally if left soaking wet in the boot of a car for a week or so, but that's no way to treat essential safety gear anyway.
Crewsaver products tend to be made of heavier material and have a more robust feel. Definitely worth the extra money if you are going to be using them every day. For leisure use the cheaper ones are absolutely sufficient. I have six XM brand auto jackets that we have been using for years with no problems.