Currently the rebreather is utilised in navies throughout the world by shallow water mine counter measures and mine clearance divers and for the deployment of combat swimmers.

I have been fortunate enough to be a test diver on most of the rebreather sets in service as well as those in production for the best part of 10 years and have seen almost every type of complication and accident that can happen.

The question posed here is, does the recreational diving instructor have the time and ability to train a student to safely dive on a rebreather? To highlight the military training trends worldwide, the student must complete in the region of 100 diving hours before he becomes competent in the use of the diving set and only thereafter is he deemed competent to handle any emergency that may arise. It must be noted that this diving is done on a daily basis over a period of 6 to 8 weeks further more he is required to remain in date on the equipment with a minimum of 6 diving hours per quarter or be subjected to a retest.

Although the recreational diver is not required to be on the same level as the military diver the emergencies remain the same and a diver well drilled in these situations is required.

Some of the common complications are:

• CO2 poisoning.
  
• O2 poisoning.
  
• Flooded scrubber
  
• Over breathed bag
  
• Free flowing demand

Instructor experience is another factor to be considered and again I will refer to the military instructor who is required to have a minimum of 2 years experience and 200 dived hours on the rebreather before he is even considered for an Instructor status.

Obviously the rebreather has very many plus points namely:

• A long endurance, typically on a closed circuit oxygen set where a fit diver can dive for a period of up to 3 hours using a 1.5l cylinder.
• Silent operation, as all bubbles are eliminated allowing hearing to be improved.

However a rebreather system has as many negative aspects to it especially the specialist maintenance required and exorbitant cost of operation where it comes to scrubber refills and gas mixes.

Rebreathers are divided into 2 categories:

• Closed circuit, meaning that the breathing loop is completely sealed and no gases are allowed to escape. This system works purely on an air demand system.
• Semi closed circuit, meaning that the loop allows an element of the gasses to escape and the air flow is set at a constant rate dependant on the gas mix.

Before even contemplating a rebreather course or instruction learn from the lessons of the past and carefully consider if you are competent and experienced enough to do it. Do not allow "machismo" get in the way of your thoughts and consider it a blemish on your diving experience, rebreather diving can be great fun but when things go wrong it is chaos.