Does your team still backmount your redundant gas? -

Does your team still backmount your redundant gas?

Article by Aaron Bradshaw, Air Hogs Scuba

You might be thinking to yourself right now that there isn’t an alternative or this author is wrong. Most teams mount their redundant gas supply via a bracket or strap system to their primary scuba cylinder. There’s an ever-growing array of products and solutions out there to mount a smaller cylinder to your primary cylinder. Different straps, buckles, metal quick-disconnect mounts, etc.

Is there a better way?

In order to answer this question, let’s look at some of the pros and cons of mounting it pony style on the back, how we got to this solution and any alternatives.

Pony Mounted Redundant Gas Pros/Cons

With the cylinder in the rear, it is out of the way of the diver and is part of the unit of gear that is donned with the BCD. This means that the diver doesn’t have additional bulky equipment in their arm range of motion. It also means less ability to manipulate the valve. The size of the cylinder for this redundant gas is also limited. Normally, this is a 19 cu. Ft. cylinder with a normal maximum being 30 cu. Ft. The gauge is also many times a button gauge, and the current gas supply is not visible to the working diver. This becomes more important as many teams move to switch blocks, and the diver has less indication that the diver is breathing off their redundant gas rather than their primary back gas.

Rear-mounted, yoke valve ponies also prove to be a significant entanglement hazard. I was lucky enough to recently participate in an ERDI Confined Space Operations course with multiple teams. The first day in the pool, the yoke knob and rear-mounted ponies presented multiple entanglement challenges. These were hard for the working divers to mitigate. We had stage-rigged AL40’s that were swapped in.

Alternatives

To assess alternatives and use lessons learned from other disciplines of diving, we can look at technical divers. How do they handle multiple cylinders, with the ability to monitor their gas supply in each? Are there lessons learned in that discipline that we can use? Can we adapt how technical divers handle deco cylinders and stages to Public Safety Diving? My answer would be yes. We’ll examine some of the pros and cons here and delve into some growing pains that I experienced in adopting this on my team.

My team now has the benefit of having membership, instructors, and mentors from other teams that are technical divers. When I joined, the team was still in back inflate jacket BCDs, back-mounted pony bottles and some antiquated methods. The truth is, in many cases, we just didn’t know there were alternatives.

We started out by moving to gas switch blocks on our full-face masks. This made it much less likely that we would have to break the encapsulation layer that provides. We then added screw-down quick connects onto our hoses supplying switch blocks. Now we had the ability to hot-plug gas into a diver in need. So then how do we mount that cylinder?

This is where stage rigging came into play. The team has moved to AL30 and AL40 cylinders that are rigged just like a stage or deco cylinder that technical divers use. With jacket BCDs, there were fewer D-Rings and options to efficiently sling the cylinder. With the team’s move to Backplate/Wing (BPW), this was no longer an issue. Most teams in our area have, and we all have compatible fittings and solutions. If a diver is in trouble, I can give my backup diver a RIT bottle and plug gas into my primary diver. A diver can also use as big of a cylinder as necessary. That emergency cylinder can even be a large steel cylinder with 100+ cu. Ft. of gas for the possibly entrapped diver. Some teams may have the ability to plug surface-supplied gas in. My team has practiced bottle swaps in both open water and in the pool, including blacked out. It’s reassuring knowing there is a way to have more gas coming with a screw-down quick disconnect and flip of the switch block.

The tender also has less weight to be lifting and moving as a unit when gearing up the diver. BCD with the primary cylinder goes on, and then the redundant gas can be clipped onto the diver before the diver enters the water. The diver also has a full view of their gas supply via gauge or button gauge.

In decon mode, there’s also no need for the diver to come out of the full face mask (FFM) or open the surface valve due to gas supply. Running low on gas for decon? Just plug more gas in for the diver. No rushed decon, FFM removed, or surface valves opened prematurely, and the result is a safer diver that has less ongoing exposure.

A critical piece of the puzzle is getting proper hose lengths. Measure and plan these out. It’s hard to beat a flexible ‘seamstress style’ measuring tape and mocking up hose routing to figure this out.

This all sounds great but what are the disadvantages?

Divers need to be trained on how to properly rig, manipulate, and dive with the cylinder. It’s also in the side and front now, so it needs to be accounted for and may reduce the divers’ mobility there.

Truth is, my team almost had an insurrection when this was brought before some members not as familiar with this methodology. It was the “Why change it? We’ve always done it this way, and change is hard” mentality. Change is hard, even if for the better. We persevered and now members see the value. It is all about building that comfort level with any equipment change to build muscle memory and familiarity. The team now runs blacked-out drills to send a backup diver with gas to a simulated entrapped diver and move them onto a new cylinder.

Making the change

We’ve had great success leveraging those technical divers and instructors on our team, especially those with significant sidemount experience, to help with proper rigging, streamlining, and setup. Ensure that all active divers and tenders are familiar with the setup, rigging, and hose routing.

If you’re looking to experiment or change your team’s methodologies, you may have team members or ERDI Instructors with experience rigging and using cylinders in this method. If you don’t have this available or need resources, reach out to SDI, and they can refer you to an instructor that can help.

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