The Sentinel Rebreather

Sentinel Features

MR Diving is an Authorised Dealer for the Sentinel and Sentinel Expedition Rebreathers.

The Sentinel is an electronics-driven fully closed circuit constant PO2 design rebreather (eCCR) that provides an intelligent and easy to use life-support system (LSS)

Manufactured in the United Kingdom (UK) by VR Technology Ltd, the Sentinel provides the user with a simple Check-and-Dive™ functionality.

It uses intelligent monitoring and design experience to determine the appropriate tests and checks. Any problems or remedial action are described clearly on the full-color graphics screen.

Key features and benefits are described below:

Sentinel Rebreather - Breathing Loop

The Sentinel has a single 4.8 liter back-mounted counter lung (BMCL) attached via a quick-disconnect system to the canister head. Each end of the breathing hose attaches at the head of the canister holder with a bayonet-type connector and are attached at the mouthpiece by u-clips which allow the hoses to be rotated for adjustment.

The Sentinel comes with a bail-out valve (BOV), which is fed by the on-board diluent. The BOV is designed to provide sanity breaths before going off board and is also removable. The Sentinel uses a combined water release and over-pressure release valve (OPV) - when the unit vents it also removes any water from the system, which can also be performed manually by overinflating the loop. The design of the loop allows for easy water removal from the loop hoses by closing the mouthpiece, raising the hoses to evacuate water, then slightly over pressurizing the loop until it vents.

The balanced valve ensures the release pressure is near constant in any orientation. The canister holder consists of three compartments: the electronics head, the middle tube that holds the filter canister, and the canister base that includes the filter carrier, spring system, temperature profile monitor (TPM), and the over-pressure valve (OPV)/water dump. The Sentinel TPM displays a thermistor based bar chart of the temperature profile through the filter to give the diver information on the activity of absorbent.

The Sentinel employs a highly efficient self-packing axial canister design, which gives extended durations and is less affected by loss of efficiency associated with increasing depth.

Try Dives

Ever wanted to try the silent world of closed circuit rebreather’s to see if it is for you?

Our ever popular Rebreather Try Dive gives you the opportunity to dive the Sentinel Rebreather in open water alongside a qualified and experienced instructor.

Try before you buy or just for a fun day out and a great diving experience just contact us and we will do the rest.


We offer full training on VR Sentinel units, please contact us to discuss your requirements.

Regulators, SPG and Hoses

The Sentinel uses the highly reliable and easily serviceable Poseidon Xtreme first stage regulators. The regulators each have an Over Pressure Valve installed in a low pressure port.

The oxygen regulator supplies the oxygen injection solenoid and a multi-port gas manifold block with manual addition valve. The diluent regulator supplies the ADV and BC inflator hose, a multi-port gas manifold block manual addition valve.

Both manual addition valves offer optional kit to allow plug-in off-board gas supplies and comes standard with Solenoid and ADV cutoff slide valves. The low pressure piping consists of stainless steel plumbing and high impact resistant, flexible Miflex hoses. A 20 micron O2 filter protects the solenoid from debris.

Harness and Wing

The Sentinel uses a custom lightweight stainless steel backplate designed to fit the contours of the outer case. Included in our price and shipped with the unit are a wing style aircell and a 4-point quick-release harness. The harness is fully adjustable, even for smaller women, and includes D-rings for attaching bail-out bottles and accessories.

Physical Characteristics

The Sentinel is shipped in a fully assembled state with the exception of the hose and mouthpiece assembly, which will be in a separate bag. Our standard package includes the sturdy and low weight carry case.

The outer case is constructed of high impact plastic and serves as a strong yet lightweight shell to protect the internal components. It's held in place by four quick-release fasteners, allowing for easy access to scrubber, hoses and cylinders.

For traveling, the cylinders may be removed and the extendable base foot adjusted to shorten the length. The canister assembly can also be removed completely and carried as hand luggage on many airlines.

VR Electronics Package

Sentinel Rebreather

For the first time in a rebreather, the electronics system has been developed by a leading dive computer company. Control, setup, decompression and alarm systems evolved from the VR3 dive computer and includes proven features and design based on a considerable knowledgeable base, research, development and design for underwater computer systems.

The Sentinel has the most richly featured, integrated software for a rebreather on the market, with electronics designed for intelligent monitoring. No single electronics failure will cause failure of the complete system. Any problems are clearly described on the main and summary screens.

Calibration in ambient air ensures calibration in a known gas, that no over pressurization has occurred, and reduces the risk from improper flushing of the loop. An on-screen checklist guides the user through the pre-dive sequence. The auto set point selects the appropriate setting for current depth and dive duration.

Options allow the user to set preferences for: last stop depth, HUD brightness, deco set point, safety factors, CNS alarm level, auto set point max, auto or manual mode, HP alarms on/off, cell configuration (on/off), gas configuration options for Dil and bailout. Main screen dive data includes: PO2, depth and max depth, dive time, decompression obligation, temperature, CNS, and battery level.

The electronics head holds the 3 oxygen sensors and the battery compartment. The ADV and oxygen solenoid housings are mounted on either side of the head. The Sentinel uses 3 rechargeable lithium polymer batteries, which can be recharged at any time without a significant memory effect. Two of the batteries act as main batteries, and when they become low the third will activate as will the battery reserve alarm.

VR Banner The battery pack lasts for approximately 60 hours in light on mode and has a backup display independent from the main electronics and with an independent power source that allows the user to stay on the loop in the event of a main electronics failure. The backup is not software driven and consists of 3 separate digital voltmeter LCD displays with the ability for calibration. The backup display's independent battery is recharged as the main battery charges. Highlights of other Sentinel electronics features include:

Auto turn-on with the detection of a PO2 drop (detection of breathing) or at greater than 1.6 atm absolute pressure (detection of depth). Diver and back mounted Heads Up Displays (HUDs) configured for color blind and highly stressed divers by positioning and flashing or solid state. Vibrating alarm on diver HUD. Digital pressure sensors for monitoring of HP Dil and O2 cylinders for low levels and high rate of use; will alarm when Dil reaches the amount needed for exit. Maintains 0.4 set point in OC mode to keep loop breathable.

  • Pre-breathe screen in the Pre-dive checklist sequence includes a bar graph showing the temperature difference across the filter.
  • Auto calibration immediately triggered when sensor is replaced, ensuring calibration is in ambient air.
  • Scrubber duration analysis from an oxygen injection meter and a temperature profile monitor.
  • Valve over inject and no inject sensors to help detect sensor failure or leak.
  • Sensor percentage remaining analysis and a dynamic algorithm for automatically removing a sensor from the PO2 averaging.
  • PC Link option allows reprogramming and upgrades via downloads through the Internet as well as downloading of dive profile data with ProLink software.

Full decompression dive computer incorporating a derivative of the Bühlmann ZH-L16 algorithm with modifications to support deep stops, adjustable shallow stop depth, and dynamic decompression ceilings. An optional upgrade allows switching between the Bühlmann ZH-L16 and Varying Permeability Model (VPM)B/E algorithm.

Sentinel Expedition

The Sentinel 'Expedition' is an enhanced version of the Sentinel Rebreather. It comes fully loaded with a range of standard features not found on any other Rebreather!
  • CO2 sensor
  • BOV in line shut off
  • 5mm back plate
  • Breathing hose protection
  • Off-board gas connection kit
  • VGM decompression algorithm
  • Integral first stage dust caps
  • Fully Independent Intelligent secondary display