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Horizon FAQs

For whom is it for?

The Mares Horizon was designed for both – recreational and technical divers:
If you are not interested in technical diving but want to stay longer time at 30 metres

Take photographs of the marine life with limited amount of bubbles to frighten them away
If you think of technical diving, but don’t want to use heavy and bulky twinset and stages for deco dives to 40 metres
If you are considering rebreather diving- but are afraid of the complexity of CCRs
Then the Horizon SCR is your choice...

Advantages of diving the HORIZON SCR 

  • The Horizon offers incredibly extended dive time compared to open circuit dives, giving the diver ample time to take in the wonderful underwater environment. 
  • Dive times are an average of 3-8 times longer 
  • Standard nitrox gas cylinders available at the dive destination can be used 
  • One or two Nitrox gases diving possible


The lightweight system is the ideal travel companion and does not require dedicated cylinders or weights.
The unit’s simple logistics allow the diver to use standard nitrox cylinders that are easily obtained from most dive destinations. 

  • Complete unit weighs only 12 kg for easy transportation 
  • Comes with one bottom gas regulator set weighing 1.4 kg 
  • Optional decompression gas regulator weighing 1.4 kg is also available 
  • Combined, the Horizon unit and regulators should fit in a single suitcase, weighing less than 23kg in total –
  • The standard checked baggage allowance for most airlines is 23 Kgs

Is it as easy as nitrox diving? 

The Horizon SCR training builds on a foundation of open-circuit and nitrox diving knowledge.
The Horizon SCR controller intuitively maintains programmed nitrox mix, depending on upon the diver preferences.
Fewer bubbles allow wildlife enthusiasts to experience closer encounters like never before.
The gas mix can be changed during the dive (using the controller) to extend dive time or decrease decompression time
The controller will warn the diver if an inappropriate gas mix exists

Creates a natural diving position 

The Horizon SCR provides warm and moist breathing gas, and an ergonomic design that intuitively improves the diver’s trim position and comfort.
The shape of the Horizon unit provides the ideal, horizontal trim
The combination of warm gas and improved dive position makes breathing natural and effortless
The specially contoured, ergonomic unit includes a soft back plate, lumbar support, buttplate and padded harness straps

What is the Fail-safe gas operation? 

The Horizon SCR was designed to maximize safety and ensure exceptional performance using multiple back-up safety systems and three sets of redundant electronics and power supplies.
A smart, diver-adjustable HUD visual indicator informs the diver of their gas supply status using a pulsing LED light.
In the unlikely event of an electronic shutdown, the diver can switch to the BOV, ensuring a continuous and safe supply of breathing gas.
During a total system failure, the unit supplies an open circuit nitrox breathing gas mix
A sophisticated monitoring system informs the diver of how much time remains before they must replace the scrubber material
Regulator set(s) provide alternate gas sources that can be shared in an emergency situation

Easy to assemble and prepare 

One of the key attractions of the Horizon SCR is its incredible ease of use.
It is simple to set up, requires no tools, has easy access to the scrubber canisters for filling, and has non-interchangeable, color-coded, quick release corrugated breathing hose connections.

No tools required
Harness can be fully adjusted according to need
Nitrox cylinders can be obtained at the dive centre upon reaching your destination
No pre-packed scrubber cartridges required – scrubber canisters can be re-filled by the diver
No dedicated weights are required

Ready for advanced divers 

For the more advanced diver, the Horizon offers a range of advantages.

As well as a longer dive duration, the diver has dual gas possibilities – with the option of attaching a second cylinder with a higher O2 concentration for accelerated decompression.
Uses the ZH-L16C Bühlmann algorithm with gradient factors
Programmable bottom gas and decompression gas
Within operational limits (up to 40m) the unit provides decompression obligations like that of a closed-circuit rebreather

Intuitive interface 

An integrated controller completes the Horizon, with a 70mm, easy-to-read color display. This intelligent computer is effortlessly operated via two large piezo elements, especially when wearing gloves, and includes a scrubber monitoring system to keep the diver informed of their scrubber status at all times, and an audible warning alarm.

Dimensions and Weight 

Height: 54 cm
Width: 40 cm
Thickness: 22 cm
Empty weight: 12 kg
Weight with filled scrubber canisters: 14 kg

How does it work?

The Mares Horizon is designed with one clear purpose: simplicity!  

It is easy to setup, transport, dive, and maintain, since every component of the unit is accessible by the user.
The unit’s internal components are easily accessed by removing the scrubbers that are located under the main outer cover.
To keep everything small and light, the gas supply for the unit comes from one or two off-board cylinders, which gives the diver an experience similar to sidemount diving.

Mares Horizon is Variable Flow SCR: 

The Mares Horizon is an active SCR with variable flow rates to maintain the desired fraction of oxygen in the breathing loop.  The diver can decide which nitrox they wish to breathe on that particular dive and set it in the computer.

To achieve a constant loop FO2, the SCR unit must constantly change the flow rate from 5 to 30 l/min, depending on the metabolic rate of the diver.
The Mares Horizon maintains a minimum flow rate of 5 l/min via the orifice, at all times.

During a dive, the fraction of oxygen in the loop is constantly measured. 

When the fraction drops below the set point, an electronically controlled valve or 'Electronic Addition Valve' (EAV) opens.
This valve injects fresh gas into the breathing loop until the fraction increases to reach the set point.

The Mares Horizon is designed to allow for diving within the no-decompression limits or for decompression dives up to a maximum depth of 40 metres.

To accelerate decompression, two different gas mixes can be used; bottom gas and decompression gas.
The bottom gas is used during the descent and bottom phase of the dive and the decompression gas is used for the decompression phase of the dive.

Both bottom and decompression gases must meet the following criteria: 

  1. Minimum Oxygen Content: 30% 
  2. Maximum Oxygen Content: 100% 

The Dive Controller (DC) 

The Mares Horizon Dive Controller (DC) is a high end, reliable dive computer that also plays an important role in configuring and executing dives with a variable flow SCR.
The DC allows the user to enter breathing gas data as well as defining oxygen fraction setpoints to maintain during the dive.

Alarms and warnings 

A warning is issued if any dive parameter is outside of its expected operating range.
These warnings are displayed in situations where the diver’s life is not in danger
An alarm is displayed if a life-threatening situation should occur.
This is a serious and potentially dangerous situation and the diver should take immediate action when an alarm occurs.

The BOV  

In case, there is a problem with the Mares Horizon, the diver can switch to breathe from the BOV.
The bail-out valve, or BOV, is a device that allows an SCR diver to close their breathing loop while automatically switching to a small but high performing built-in second stage regulator that allows the diver to breathe in “open-circuit”, eliminating the need to remove the breathing loop from the mouth should the unit malfunction.
The BOV uses the same gas that supplies the rest of the unit.

Scrubber absorbing CO2 

The only job of the scrubber material is to remove Carbon Dioxide from your exhaled breathing gas.
The Mares Horizon has a unique dual-scrubber system that uses two scrubber canisters mounted in sequence to allow gas to flow from the upper scrubber to the lower.

For more information concerning particular procedures or components of the Mares Horizon SCR, to arrange an inspection or pre purchase try dive, please call the Dive Centre on 61+2 4389 3483