So Your Diving with an Inspiration wearing Buddy, Here's the Low-down on what to expect

Prior to Diving

The big difference here is in the pre -dive checks that an Inspiration user MUST do. On your open circuit set, you'll probably get away with just turning the gas on and going diving. This is not true on a rebreather. Each user will have a set sequence of tests they MUST do before entering the water, even if its only 5 mins since they come out (even more so in that case). Don't worry they wont take long and are carried out in addition to the normal buddy checks which still need to be done. One of the myths of rebreathers is that they take ages to set up. This is not true

Positive Inflation Test. 

The units buoyancy compensator and breathing loop are filled to maximum pressure, sealed and left for a time. They must not deflate. This tests for air leaks. This test is often done well before kit up time. The lung dump valve is tested at this time also (Min 3 mins)

Negative Inflation Test

The units breathing loop is sucked free of gas and sealed for a time. Often a hose is crushed. The system must not draw air back in and expand for some time. There should also be an audible gush of air into the mouthpiece when it is opened after the test. Again this tests for air leaks. This test is often done well before kit up time (Min 3 mins)

Diluent side Checks

The diluent cylinder is turned on, the pressure gauge checked to make sure it has enough gas and the diluent injector tested (also the ADV if fitted). The fitted bail out DV should also be tested along with the buoyancy compensator and drysuit direct feeds. (30 seconds)

Oxygen Side checks

The oxygen cylinder is turned on (SLOWLY) and the pressure gauge checked to make sure there is enough gas. The Oxygen manual injector is also tested. (60 Seconds)

Electronics and initialisation

The master handset is turned on. There should be audible beeps to confirm the beeper works and then a click as the solenoid and batteries are tested under load. This test should always be done with the O2 on and pressurised to be meaningful. The slave handset is then tested in the same way. The user will then proceed through the electrics initialisation routines to get the handsets into dive mode. This may (and should daily) include a calibration check. They may also need to calibrate their computers (min 1 min, max 5 mins). This check is computer prompted and should involve another check of all valves

Pre-breath

The last and the most important test is to breath from the unit for at least 3 minutes prior to diving. This way if something is malfunctioning they will go unconscious while on the boat/shore and not in the water. This test is the most important and is a real lifesaver. Don't dive with them if they don't do it.

Checks for you to do

Do check up on your Inspiration equipped buddy
1) Ask to see his contents gauges and make sure the gases are switched on and their is enough. Query him if they are not both full
2) Listen to hear if there are any warning beepers sounding. If they are then something is up and the unit is NOT divable. Do not accept any excuses
3) Check if he is carrying sufficient Open circuit bail out gas to abandon the dive at any point and complete the required decompression
4) Learn how to close his mouthpiece. if you have to rescue him you must close this if you remove it from his mouth as otherwise the loop will flood and loose buoyancy
5) Most importantly. Is he pre-breathing from the unit and has he been doing it for at least 3 mins. Don't dive if he isn't (this most simple check would have saved many lives if carried out)

During the Dive

Descending

This is a time of high task loading for the rebreather diver. As well as clearing his ears and filling the dry suit, he will need to monitor his handsets, inject diluent into the lungs and at some time swap from his low set point to high set point. He should also perform a stop at around 6m to check for bubbles and leaks (a good practice on OC). The main risk here is descending so fast that the O2 level raises too quickly. Most rebreather divers are slower on descent than OC divers

Bottom

Once on the bottom the rebreather diver will settle down. The unit works best at constant depth and so the only differences will be that a) your buddy swims around object rather than over and b) they should be checking their handsets regularly (about once a minute). There should be no bubbles from the unit at constant depth. Most rebreather units will practice some drills at some time on most dives. Make sure that your buddy does check his handsets much more regularly than you check your contents gauge

Ascending

OK, now you will see some bubbles. As you ascend the rebreather diver will need to vent some of the expanding gas. he may do this several ways 1) through the lung dump valve (uncommon), 2) breathing out through his nose (common) or 3) breathing out through his mouth around the mouthpiece (common). He also needs to keep an eye on his gauges as as the pressure drops the PPO2 will lower. This is again on top of decompression and normal ascent constraints. So again this is a time of high task loading. On the surface he needs to continue to monitor his handsets

Post dive

The unit must be kept upright or laid on its lungs. Never on the yellow back. This keeps the internal condensation away from the Sensors. The buddy may need to turn off the electrics and gases if there is a wait before diving again. If its the last dive then he may remove the scrubber contents and dry the electrics. If it is being dived again on the same scrubber contents the mouthpiece is left shut to stop airflow. The exhale lung may be drained of fluid that has collected.

Some advanced points

THINGS AN OC BUDDY SHOULD KNOW
How to open and close the CC mouthpiece, the operation of the diluent and O2 manual inject valves, (but normally leave the latter well alone), and recognise the terms and symptoms of hypoxia, hyperoxia and hypercapnia. This is within the skill-set of BSAC Sport Diver and above, but would probably not be appropriate for anything less than a PADI Rescue Diver.

There are numerous modes of failure of a rebreather. Most are simple to spot if the checks are done. But if not the first warning you may get as a buddy is hearing a warning beeper. If this happens you must ensure that the rebreather diver takes steps to rectify the problem. He should at least inspect his controls and analyse the situation. Give him an OK while pointing at the handsets and expect one back. Unfortunately the second symptom of failure is normally unconsciousness. What can you do in that case

a) Get him on a known gas supply. If conscious swap him to his bail out system and begin an ascent immediately. Make sure his mouthpiece is closed. If unconscious then flush his system with diluent while venting and begin to surface immediately

b) If you can inspect a handset check to see if the O2 is high or low. If low make sure his oxygen is turned on. If high continue on the diluent or bailout.

If in Doubt Bail him out!

PROBLEM	CAUSES	CC DIVER RESOLUTION	OC BUDDY RESOLUTION
Low Oxygen	Solenoid blocked	Use O2 manual inject	Diluent flush or offer bailout / octopus, then diluent inject every third breath, then rescue to surface
	O2 cylinder valve / electrics switched off	Switch them back on	Diluent flush or offer bailout / octopus, check O2 cylinder valve / electrics are on, then rescue to surface
	O2 cylinder empty or no access to O2 at all	Use diluent flush, then go to diluent based semi closed mode	Diluent flush or offer bailout / octopus, then diluent inject every third breath, then rescue to surface
	Fast ascent	Add O2 manually or diluent flush, slow the ascent	Diluent flush, slow the ascent, offer bailout / octopus, then diluent inject every third breath, then rescue to surface.
High Oxygen	Solenoid jammed open	Diluent flush and switch O2 cylinder valve off, use valve to control injection of O2	Diluent flush and switch O2 cylinder valve off, offer bailout / octopus, then diluent inject every third breath, then rescue to surface
	Accidental O2 manual injection!!!	Diluent flush	Diluent flush, offer bailout / octopus, then rescue to surface
	Fast descent	Diluent flush and slow the descent	Diluent flush, offer bailout / octopus, then rescue to surface
Full Electronics Failure	Water ingress, batteries flat, broken something, etc.,	Use diluent flush, then go to diluent based semi closed mode	Diluent flush or offer bailout / octopus, then diluent inject every third breath, then rescue to surface
Stack Flood / caustic cocktail	Leakage of water into scrubber housing	Switch to OC Bailout	Offer bailout / octopus, then rescue to surface

 

Rebreather divers can suffer from decompression sickness, burst lung and all the other diving injuries. Treatment is exactly the same as for an open circuit diver

BSAC Recommendations (Fairly Sensible)

It is important to ensure the rebreather diver is partnered with a buddy who can assist them in the event of a problem. Therefore, the BSAC recommends that the;

The buddy should be preferably another rebreather diver diving the same rebreather,

If the buddy will be an open circuit diver then;

A buddy of a rebreather diver (whether SCR or CCR) should be, as a minimum, an experienced Sports Diver with their DO's consent
The DO (or DM acting on behalf of DO) should ensure that the Sports Diver who will buddy a rebreather diver is;

    experienced under the current diving conditions (i.e. site and weather)
    capable of recognising the conditions of hyperoxia, hypoxia and hypercapnia
    capable of performing a rescue (CBL and surface support) on the rebreather diver in the case of an emergency

The buddy of any rebreather diver should wear a redundant configuration if diving deeper than 20 m.
The capacity of this redundant supply should suit the depth of the dive being undertaken.
The buddy should carry a D-SMB (or SMB as appropriate) and at least one other surface detection aid
The buddy check procedure must be modified to accommodate the rebreather layout especially the shutdown operation of the mouthpiece.
Buddies should have preferably attended a BSAC Rebreather Awareness Course,

Dive Marshal
The dive marshal or deputy dive marshal should have:

Minimum qualification of Nitrox Diver / Advanced Diver
Preferably attended BSAC Rebreather Awareness Course

Must know the following information:

Dive plan (i.e. time and direction)
Max ppO2 setting and planned MOD
Surface detection aids carried
Size and content of all tanks (diluent, oxygen and additional bailout)
Remaining duration of scrubber material
Maximum duration of Nitrox tank (excluding 50 bar reserve)