Halcyon RB80

It was originally developed by Reinhard Buchaly (RB) in 1996 for the cave exploration dives conducted by the European Karst Plain Project (EKPP).

[1] The Halcyon RB80 was introduced as a replacement for the much bulkier and more mechanically complex PVR-BASC, which was depth-compensated and used a ballasted bellows counterlung.

[1] The RB80 passive addition semi-closed rebreather was originally developed by Reinhard Buchaly (RB) in 1996 for the cave exploration dives conducted by the European Karst Plain Project (EKPP), and is approximately the size of the common 80 cubic foot aluminium scuba cylinder.

Between January 2018 and December 2020, MCEP divers mapped more than 180,000 metres (590,000 ft) of new cave passage in Sistema Ox Bel Ha using RB80s.

[1] The RB80 has also been used for cave exploration projects in China, Australia, the south of France, Spain, Italy, and other karst areas around the world, and has also been used for ghost net removal and for wreck diving.

The pressure drop draws the contents of the outer bellows through the scrubber, inhalation hose, non-return valve and mouthpiece to the diver.

The design of internal ducting leads water in the exhalation side of the loop into the inner counterlung bellows, and from there it is discharged to the surroundings along with the gas during the inhalation stage of the cycle.

[4] The RB80 is usually carried between a set of back mounted isolation manifolded double cylinders, supported on a backplate and wing harness.

The deficit will vary at constant depth with the ratio of respiratory minute ventilation to rate of oxygen consumption, as will occur in hyper- or hypoventilation.

The variation in oxygen deficit means that the range of depth at which the rebreather is safe to dive is significantly less than for the same supply gas on open circuit.