CUMA (Canadian Underwater Mine-countermeasure Apparatus) (commercially called SIVA+) is a make of rebreather underwater breathing set designed and made in Canada for the Canadian Armed Forces by Fullerton Sherwood Engineering Ltd to replace the Royal Navy CDBA.^[1]

The unit consists of a back mounted casing, containing its: carbon dioxide scrubber, oxygen supply, diluent supply (both spherical flasks), a mechanical ratio regulator, electronic PPO2 monitoring, and all of the valves and fittings. The remainder of the breathing loop consists of a pair of chest mounted counter lungs connected by the usual loop of wide corrugated breathing tubes running from and to the top of the backpack. It has a small bailout cylinder horizontally across the bottom of the backpack casing which is plumbed directly into the divers breathing loop.^[1][2]

It is a self-mixing semi closed circuit rebreather (SCR). A constant flow of oxygen is mixed with a diluent volume dependent on the ambient pressure.^[1] The deeper the diver dives, the more diluent is added, and thus the leaner the supplied breathing mix. The correct oxygen setpoint is monitored electronically and alerts the diver via a heads-up-display (HUD) if it is not being correctly maintained. The CUMA is capable for diving to a depth of 90 meters (295 feet) or a maximum working pressure of 10 ATA. It can be calibrated for the use of different diluents such as: air, trimix, heliox, or pure helium.^[1]

Its first prototype set was made in March 1987.^[1]

• Diving rebreather – Closed or semi-closed circuit scuba
• Cobham (company) – British defense industry manufacturing company

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