A rebreather is a self-contained breathing device that reuses part of each breath when scuba diving. These devices are able to recycle oxygen left unused each time you exhale while also removing carbon dioxide using a chemical that traps it. This means that it can significantly extend dive times with seemingly small tanks.

What is the difference between fully-closed and semi-closed rebreathers?

There are two major classes of rebreathers: fully-closed and semi-closed rebreathers. Each share many components of the other. However, there are some differences.

  • Gas expulsion: A semi-closed one, as part of its normal operation, expels a small amount of breathing gas regardless of the depth of the diver. On the other hand, the fully-closed one completely recirculates the breathing gases.
  • Oxygen: Semi-closed rebreathers are simpler in design and are dependent on the constant flow of oxygen and diluent or a predetermined nitrox mixture. On the other hand, fully closed-circuit rebreathers have oxygen sensors that constantly monitor the oxygen's partial pressure with change in depth. Based on this information, the rebreather adds oxygen to the breathing mixture.
Should you carry out a prebreathe test before a dive?

Many divers test their equipment before taking it underwater to ensure it works well for them, especially when it comes to breathing support equipment. A prebreathe test will help you in detecting any faults before rebreather diving, thus preventing accidents or unexpected events while on a dive.

How deep can you dive with a rebreather?

The depth requirements vary depending on the circumstances and the rating and type of unit. The depth limit for diving with fully closed-circuit rebreathers is based on bail-out requirements for the entire system. In general, rebreather divers stay below 200fsw, similar to regular divers, but have extended bottom times.

How do you maintain the rebreather?

To keep your rebreather in tip-top shape, maintenance can help you to improve its performance and extend its life:

  • Be proactive: This means doing a basic clean-up after each day of use, rather than letting moisture and dust build up over several days. After diving, get rid of the moisture in the cell cartridge and wipe down its head.
  • Keep it dust-free: Buildup of dust can create an O-ring leak and can be difficult to remove. It is easier to wipe down the canister and head clear of moisture and dust on a regular basis.
  • Disinfect: The counterlungs and rebreather loop are extensions of the respiratory system. Be sure to rinse out your mouthpiece, counterlungs, and breathing hoses with a combination of water and streamline, which is a disinfectant.