Rebreathers are more complex and expensive opposed to what ?
The possible endurance of a rebreather dive is longer than an open - circuit dive , for similar weight and bulk of the set , once a practical lower limit for rebreather size has been exceeded , and a rebreather can be more economical when used with expensive gas mixes such as heliox and trimix , but this may require a lot of diving before the break - even point is reached , due to the high initial and running costs of most rebreathers , and this point will be reached sooner for deep dives where the gas saving is more pronounced .