November 16, 2018 2 min read

by: Nick Marino PADI MI 14335 NAUI CD 39526 TDI 1838

An interesting observation I frequently make is how few divers utilize redundant air supply systems. The redundant system I am referring to is a separate cylinder, regulator, and submersible pressure gauge (mini button type is fine.)

Why use a redundant system? While not necessarily needed on shallow (35 feet or less) dives in an environment that requires minimum weighting and gear configurations, its value on deeper dives or dives requiring more exposure protection and the associated weighting requirements become apparent. Simply put you just cannot move through the water as quickly. And the deeper you are there is that much water to move through if you have a catastrophic air loss or regulator malfunction. Air sharing with a competent buddyis an option if they are close enough and you have reviewed the skill with them. Unfortunately this is often not the case. The redundant system lets you be self-reliant. A question I ask myself while I’m diving is that if I exhale and then attempt to inhale and there is no air what would I do? Could I perform a controlled emergency swimming ascent? Could I swim over to my buddy and get their attention and share air? If the answers are no or I’m not sure then I am diving well outside my comfort/safety zone.

Cylinder sizes should be 19 to 30 cubic foot capacity (aluminum). The rule of thumb here is the deeper the dive the larger the cylinder. The size should be enough so you can make a normal safe ascent and safety stop with air left over. The cylinder is mounted on the diver's right side to the main cylinder with the regulator hose (36 to 42 inch length) running under the divers right arm. The regulators second stage should be secured with a bungee style necklace around the diver's neck. A swivel on the regulator hose at the second stage will allow the second stage to hang horizontally at this location.

This set up provides a balanced positioning of the redundant air supply and reduces the chance of snagging the hose while operating in reduced visibility or around submerged objects and wrecks. It more importantly allows the diver to quickly access the redundant air supply regulator if needed.

Some divers may opt to stage the redundant cylinder under their left arm instead of mounting it to the primary cylinder. This is also acceptable.

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