Diving

Rebreathers have plusses, but know before you go

Carsten Huppertz, head captain at Florida Keys Dive Center, dives using a rebreather.
Carsten Huppertz, head captain at Florida Keys Dive Center, dives using a rebreather.

The diver silently was hovering in the hazy distance — no apparent movement — no bubbles coming from his regulator.

The image came into focus as the group of newer divers I was guiding got closer.

The diver was Carsten Huppertz, head captain at Florida Keys Dive Center, who holds an impressive list of diving instructor ratings, decked out in a rebreather, shiny “bailout” bottle and stylish black dry suit.

My thoughts leapt to a scene from a secret agent movie where the hero climbs out of the water, sheds his scuba gear and dry suit and then walks into the bad guy’s cocktail reception with his hair perfectly in place and not a wrinkle on his tuxedo.

After the theme from the James Bond movies finished playing in my head, I checked on my divers flapping through the water and made the underwater turn back to the dive boat.

“Who knows, maybe I will get to see Halle Berry climb out of the ocean,” I thought.

In 1943, Jacques Cousteau and his partner Emilie Gagnan co-invented a demand valve system that supplies divers with compressed air when they breathe. The exhaust gas is discarded in the form of bubbles; this is called an “open-circuit" system, and has become synonymous with what many know as SCUBA, an acronym for Self-Contained Underwater Breathing Apparatus.

The standard scuba setup has worked well since the advent of recreational diving.

It turns out, however, that rebreathers have been around longer than better known open circuit scuba gear. Henry A. Fleuss submitted a patent in 1878 and the rebreather was used two years later to close some crucial valves in the Severn River.

Since the days of Cousteau, most recreational scuba divers have used: a mask to enable them to see underwater; a tank containing compressed air (regular filtered air, not oxygen); a scuba regulator, which provides air at the appropriate pressure needed at different depths; fins to swim efficiently in the water; exposure protection (wet suit) to keep them protected and warm; a dive knife to be used as a tool – not a weapon; a depth gage and timing device (both of which are now available in underwater computers); and a compass for navigation.

Added to this are a buoyancy control device (BCD) to help divers float at the surface or to maintain neutral buoyancy underwater (like a fish), and lead weight to help counteract the buoyancy characteristics of their bodies and wet suits.

As Bob Dylan sang in 1964, “The Times They Are A-changin'.”

With decreases in cost and difficulty of operation, rebreathers, once the realm of military and highly-trained specialty technical divers, are becoming increasingly popular with recreational divers.

A major benefit of a rebreather is longer dives, because a portion of the gas supply is reused, than when using open circuit scuba tanks.

Rebreathers are great for photography because they don’t frighten fish with exhaust sounds. And, they deliver warm, moist breathing gas and a more optimum gas mixture for divers on extended and deeper dives.

There are three basic types of rebreathers: oxygen rebreather, semi-closed rebreather, and closed-circuit rebreather (CCR). Some experts and manufactures differentiate the types into two or four. Halcyon, a dive equipment manufacture, lists oxygen, active addition, semi-closed passive addition and fully closed. ( http://www.halcyon.net/en/gear-up/rebreathers/rebreather-types)

The difference in the method rebreathers operate is the manner in which they add gas to the breathing loop, and control the concentration of oxygen in the breathing gas.

Generally, the breathing loop includes a carbon dioxide (CO2) absorbent canister, a way to add fresh oxygen needed by the diver, and a design to ensuring that gas circulates in one direction. A single fill of a small gas cylinder or cylinders and CO2 scrubber can last, depending on the model, from one to six hours; and, gas duration on a rebreather is nearly independent of depth allowing a diver to spend more time at the deepest portion of a dive.

Rebreathers can be more expensive to purchase and operate than a traditional regulator, BCD and scuba tank setup.

Additional training is also required to use a rebreather, even if you are already a certified diver.

Several dive organizations teach rebreather and technical diving. One of the oldest and largest is Technical Diving International (TDI): https://www.tdisdi.com/tdi/who-is-tdi/.

Another, the Professional Association of Diving Instructors (PADI), is the largest trainer of recreational divers. Its site relating to rebreathers can be found at: https://www.padi.com/padi-courses/rebreathers

The PADI Rebreather and Advanced Rebreather Diver courses use type “R” units to introduce divers to rebreather diving within recreational dive limits. These units are electronically controlled and provide a backup for all the major systems, which simplifies training and use.

According to PADI, type R rebreathers, which specifically are “suited for recreational diving”: will not operate or will warn the diver if the canister is missing; provide electronic prompts for the predive check; provide automatic set point control; estimate scrubber duration; and, have warnings for low or closed gas supply.

They also display low battery life and high or low PO2 (percentage of oxygen); include a “black box” data recorder functions in the electronics; and; have a display warning system in line-of-sight during normal diving.

PADI’s more advanced Tec CCR courses teach technical divers how to use type “T” closed circuit rebreathers beyond recreational dive limits. (For a list of requirements for type “T” rebreathers see: https://tecrec.files.wordpress.com/2013/01/type-t-rebreather-specifications-v1-4.pdf

The Keys is fortunate to be home to Georgia Hausserman, an expert in the field of rebreather training. Georgia is a member of PADI’s Technical Diving Division and Rebreather Advisory Team, and has helped develop an instructor and instructor trainer base for PADI’s rebreather and CCR programs.

Gary Mace, who with his wife Brenda own and operates Conch Republic Divers, holds rebreather instructor certifications with PADI and the International Association of Nitrox and Technical divers (IANTD).

According to Mace: "Rebreathers are a wonderful tool when used properly within a diver’s certification level and experience. I’ve got friends who have explored shipwrecks down to 340 feet for up to an hour using this technology, which would be very difficult or impractical on open circuit."

As with any type of diving, when diving with a rebreather, you should make sure your gear is in good working order and properly checked before each dive. You only should dive to the limits of your training and be conservative in your dive(s). Don’t let the pressure of “getting one more dive” or another person’s urging influence your decision to dive.

Upper Keys dive shops providing rebreather training include Conch Republic Divers (http://conchrepublicdivers.com/) Rainbow Reef Dive Center ( http://www.rainbowreef.us/) and Horizon Divers (http://www.horizondivers.com/).

A comprehensive list of diver certification agencies is available at: https://en.wikipedia.org/wiki/List_of_diver_certification_organizations#Technical_diving_certification_agencies

Don Rhodes, in addition to a career in government affairs, has taught scuba for 30 years. He and his wife retired to Tavernier five years ago, where he works as an instructor for Conch Republic Divers. He can be reached at donrrhodes@gmail.com.

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