Please observe that the practical knowledge may differ between different rebreathers and configurations. SwedTech Diving recommends that the students use their rebreather according to the manufacturer’s recommendations
The student must be able to assemble his closed circuit rebreather on his own and understand the configuration used.
The student must learn how to find the minimal loop volume, just before the ADV is triggered. This is performed as a start drill under calm conditions at shallow depth. During this exercise the student should also practice manually maintaining a PO₂ of 0.7 bar with the needle valve closed.
Handling of a bail out cylinder
- Switch the BOV to OC
- Signal the team
- Point to the BOV while breathing out so the team can see the bubbles and understand you have switched to OC
- Check that the bailout cylinder you want to use is available
- Check the MOD of the bailout cylinder, that it is usable at the current depth
- Open the bailout cylinder valve ¼ revolution
- Check that there’s gas in the cylinder and that there is no leaks
- Close the bailout cylinder valve
- Check that the bailout cylinder hose runs freely
- Pull out the bailout cylinders second stage with your right hand and show the full length of the hose while with your left hand showing the MOD marking to the rest of the team
- The team confirms the correct MOD with an OK sign if everything is right
- Open the valve on the bailout cylinder completely while you control your depth
- Remove the BOV and keep it to your chest and switch to the bailout cylinder regulator
- If everything is good, give the team an OK sign and the sign to abort the dive, thumbs up
- Place the diver on the bailout cylinder first
- Abort the dive according to place, time and decompression
This exercise is first done at shallow depth under calm conditions. It is important that this exercise is performed correctly.
During this exercise the student also stows the bailout cylinder and switchs back to CCR. The student must make sure that the gas is breathable before going back to CCR, lowest PO₂ is 0.6 bar.
If the rebreather lacks a BOV this exercise will be modified to suit this.
Clearing of the mask
Clearing of the mask is done the first time at shallow depth under calm conditions. The student must be aware that the buoyancy is affected while clearing the mask.
The student must be able to show good buoyancy about 50 cm above the bottom. The student must train using loop volume, wing and drysuit (if used during the course). The student should strive for being so weighted and balanced that, with minimal loop volume, just a little gas in the wing and drysuit is needed to maintain good buoyancy.
Keep constant PO₂ while swimming
The student must while swimming at a depth of 6 meters, with closed needle valve, maintain a PO₂ of 0.7 bar.
Be able to vary PO₂ while swimming
The student must, while swimming at a constant depth with closed needle valve, keep a PO₂ of 0.5 bar for five minutes. The student must then switch up to a PO₂ of 0.9 bar for five more minutes, also here with the needle valve closed. A variation of +/- 0.1 bar is allowed during this exercise.
Descents are first trained during calm conditions to a maximum depth of six meters until the student is able to stop the descent about 50 cm from the bottom.
The student must at the surface before the descent and at a depth of six meters, together with the team, be able to perform an S-drill before starting the dive.
Start the descent with a minimal loop volume and a PO₂ of 1.0 bar in the loop.
Descent can be done on the BOV if the diluent is breathable on the surface. The student should also train on descents while using the regulator from the bailout cylinder.
The student must train on manually adding O₂ to the loop during descent.
At six meters the cells are verified by checking that they read 1.6 bar. When the validation is done the student can switch to CCR. When the student has switched to CCR leak check and bubble check is made. Before descent the student must exhale from the nose to trigger the ADV to dilute the gas to 0.7 bar.
Decent should be done so everyone in the team can get attention from everyone else in the team.
The student must exhale gas with the nose to cause under pressure in the loop to trigger the ADV. With a long slow inhale the student must get the PO₂ to the equivalent PO₂ of the surrounding pressure.
I.e. if air is being used as diluent the cells should read 0.42 bar at 10 meters depth. It is important that the student read both cells during this validation.
This must, during the course and on all dives thereafter, be done at least three times / dive.
Remove moisture from the cells
The student must exhale gas with the nose to cause under pressure in the loop to trigger the ADV. With a quick inhalation gas flows passed the cells and removes moisture. This should be done as a stationary exercise and then as an exercise simulating that the cells shows different PO₂.
Go off and on the DSV
If the DSV is equipped with a BOV the student should first switch to OC. The student takes the DSV out of his mouth. The student goes back to the DSV. Before switching the BOV to CCR the student must check that the gas in the loop is breathable by checking the PO₂.
If the DSV does not have a BOV the student must understand the usage of this and this must be practised before the bailout drill.
Removing water from the loop hose
The student compresses the bellow hose between the DSV and the right T-piece.
The T-piece on the right shoulder must be the highest point on the diver for this exercise. This is easiest performed using a slightly vertical position in the water. Lean your head to the right and blow the water down in the right counter lung. This may be needed to done a couple of times for the student to find the right position.
This should be done as a stationary exercise and the student should do it when needed or as the instructor added exercise.
Loop flush or diluting of high PO₂ is performed when a high PO₂ quickly must be lowered.
The student is striving for a position in the water where the ADV is the lowest point of the diver and the highest point the right counter lung dump valve the highest.
It very important that the student do not open the dump valve before there is a considerate over pressure in the counter lung. This is to prevent water getting in the counter lung and the rest of the rebreather.
The left hand is used to open the dump valve and the right hand alternately squeezes the loop hoses behind the T-piece.
This should be done as a stationary exercise and then as a part of an exercise simulating high PO₂.
Removing water from the loop
The loop needs to be over pressurised for water to be able to escape through the dump valve. The over pressure is either created by using the ADV or with separate bail out gas.
This exercise is done in a vertical position in the water. Empty the wing and drysuit from gas. Trigger the ADV with the purge button on top of the canister with your left hand while you pull the dump valve on the counter lung with your right hand.
If the student cannot reach the purge button on the ADV the student can draw gas from bail out, BOV or separate bail out cylinder and blow in the loop.
The student may physically hold on to an object in this exercise to prevent from losing buoyancy.
Ascents are first being practised from shallow depths and then progressively deeper.
During the ascent it’s very important that the student checks his PO₂. PO₂ should not sink below 0.7 bar during the movement during the ascent. On the safety stop the PO₂ should be at least 1.2 bar.
The wing and drysuit is emptied early during the ascent. It is better to work with a bigger loop volume during the ascent as the risk of triggering the ADV is lower which will lower the PO₂. During the ascent the expanding gas is vented through the nose.
The student must learn the relationship between exhaled gas and how much oxygen needs to be added to maintain PO₂. The student must also be trained how buoyancy is maintained during the ascent by dumping excess gas through the nose and addition of oxygen.
Ascents are also trained in bail out scenarios. Here the ascent is done on the separate bail out cylinder. The student must in this scenario remember to dump expanding gas from the loop in the same was as in the wing and drysuit. Expanding gas is dumped using the dump valve on the right counter lung. If gas is dumped from the DSV the student must make sure that the pressure in the loop must be higher than the surrounding pressure, otherwise the rebreather will be filled with water.
Simulated decompression procedure
The student must perform a simulated decompression scenario from 25-30 meters depth with stops at 21, 18, 15, 12, 9 and 6 meters. The times for the stops should be at least one minute between 21 and 12 meters, at least three minutes at 9 meters and at least five minutes at 6 meters.
On the stops between 21 and 12 meters the student must maintain a PO₂ of at least 1.1 bar.
On the stops between 9 and 6 meters the student must maintain a PO₂ of at least 1.4 bar.
At the surface or in shallow water the student must, while swimming, maintain a PO₂ of 0.7 bar. The needle valve is adjusted until no additional oxygen needs to be added manually. Exit the water and measure the flow with a flow meter. Note the metabolism rate.
When the student enters the water the flow is slightly lowered.
Handling of the needle valve
The needle valve is adjusted so the PO₂ is slowly sinking. The student must learn how many turns the needle valve needs to be opened to give the right flow. The student must be able to operate the needle valve by touch only without having to look at it.
Handling of bail out cylinder
The student must be able to move the bailout cylinder between the default position, and nose clipping it to the hip D-ring. The student must also be able to hand over a bail out cylinder to other team member.
The student must be able to shut off and turn on both the oxygen and diluent cylinders on the rebreather within 60 seconds.
The student must train on using the rebreather as a SCR in the case of running out of oxygen. The student must shut down the valve for the oxygen while in CCR and then swim while exhaling each second breath through the nose. It’s important to monitor the PO₂ all the time.
Oxygen leakage / free flow
The student shuts off the valve to the oxygen cylinder. The needle valve is opened fully to simulate free flow. The student trains to open and close the oxygen valve to maintain a predefined PO₂ set point.
ADV leakage / free flow
The student must be able to handle a free flowing ADV. During this exercise the instructor simulate a free flowing ADV by pressing the purge button on the ADV.
The student must shut off the diluent valve. A follow up problem from this could be too high PO₂. The student should solve this by exhaling through the nose and then quickly open the diluent valve to add diluent to lower the PO₂.
Handling of an SMB
The student must be able to send up an SMB in a safe and controlled manner within two minutes. The ascent is done with the line from the SMB as a reference. The spool must be reeled in during the ascent. During the ascent the spool may be used as depth reference if locked to the depth where the current stop.
Diving in team
Understand and use the advantages of diving in a well-balanced team and to be able to see and solve problems before they escalate or generate follow up problems.
The student must be able to understand and use the standardised hand signals at the correct times.
The student must be able to understand and use the standardised light signals at the correct times.
The student must be able to understand and use the standardised touch signals at the correct times.
Handling of free flowing wing inflator
The student must be able to shut-down and disconnect a free flowing wing inflator without varying more than 50 cm in depth.
The student must be able to use and vary the different swimming techniques according to the circumstances regarding the dive. He must be able to swim backwards 10 metres and do a helicopter turn at least 360 degrees in each direction.
The student must be able to lie still in a horizontal position without varying more than 50 cm in depth with the bottom as reference, or in an ascent a shot line as reference.
Rescue of paralysed diver
The student must rescue a diver from at least 15 meters depth and together perform a safety stop between 3-6 meters for one minute. After this the diver must tow the rescued 50 meters.
Before the ascent check PO₂. in the student should ensure the loop mouthpiece remains in the paralysed diver’s mouth. Remember that the diver doing the rescue must take care of the buoyancy for both divers during the ascent. The student must also make sure to dump excess gas from the paralysed diver’s loop.
At the surface positive buoyancy should be made and help should be called.
Analysis of gas
The student must analyse their gas and calculate the MOD before each dive.