Chapter 19, Us Navy Dive Manual, Rev 6

Front 1

While diving the Mk25 you experience symptoms of hypercapnia. What is your course of action?

Back 1

Increase ventilation if skip-breathing
Decrease exertion level
abort the dive. Return to the surface and breath air.
During ascent, maintain vertical position and activate bypass valve, adding fresh O2.

Front 2

When planning a MK25 dive, what are the operating limitations that must be considered?

Back 2

UBA O2 supply
UBA canister duration
O2 exposure limits
Thermal factors

Front 3

When diving the MK25, what is the recommended objective swim speed?

Back 3

Swim at a relaxed, comfortable pace. Usually around .8 knots.

Front 4

What is the advantage of the turtle back technique?

Back 4

maximizes operational range by swimming on the surface part of the time, breathing air where feasible.

Front 5

What is the minimum personnel requirements by position for conducting a MK25 dive.

Back 5

Diving Supervisor/Boat Coxswain
Standby diver in SCUBA
DMT or individual trained in diagnosis/emergency treatment of diving injuries
MK25 dive pair.

Front 6

Once the pre-dive set-up has veen performed on the MK25, explain the configuration the rig is placed in for transportation or storage?

Back 6

Close O2 cylinder
Vent system
Deplete the breathing bag
Close the dive/surface valve
Store the checklist with the rig.

Front 7

When diving the MK25, conducting a proper purge prevents the possibility of what diving malady?

Back 7

Hypoxia

Front 8

When diving the MK25 what are the causes of hypercapnia?

Back 8

CO2 absorbent failure
Inadequate ventilation
Excess exercise rate
Canister flooding

Front 9

During the purge procedure on the MK25, what common mistakes must be avoided?

Back 9

Exhaling back into the bag.
Under-inflation of the bag
Lack of room for bag to expand.
Breaking the seal of your mask.

Front 10

When filling the Sodalime canister with CO2 absorbent, why is the last one inch of absorbent in the container not used?

Back 10

Due to absorbent dust accumulating at the bottom of the container.

Front 11

When donning the MK25, why should the harness be adjusted to a loose fit?

Back 11

To allow adequate space for the breathing bag to expand.

Front 12

How long must you wait after a MK25 dive before you are eligible to fly?

Back 12

Flying is permitted immediately after O2 diving unless the O2 dive has been part of a multiple UBA dive profile in which the diver was also breathing another breathing mixture.

Front 13

On a transit with excursion dive profile, how is the "excursion time" calculated?

Back 13

Only a single excursion may be taken at any time during the dive.
1-20 fsw: 240 Min.
21-40 fsw: 15 Min.
41-50 fsw: 5 Min.

Front 14

Describe your course of action as a MK25 diver who has exceeded the depth and/or time of excursion limits?

Back 14

Dive may be aborted.
Dive may be treated as a single-depth dive applying the maximum depth and total O2 time to the Single-Depth Limits.

Front 15

What is the correct procedure for managing a convulsive diver?

Back 15

1. Assume upright position behind diver. weight belt should be left on to prevent diver from assuming face down position on surface.
2. Leave mouthpiece in mouth. If not in mouth, do not replace it; however, ensure the mouthpiece is switched to the surface position.
3. Make a controlled ascent to the surface, maintaining a slight pressure on the diver's chest.
4. If additional buoyancy is required, activate the victims life jacket.
5. Upon reaching surface, inflate the victims life jacket.
6. Remove the mouthpiece and switch to surface to prevent rig flooding and weighing down victim.
7. Signal for pickup.
8. When convulsion has subsided, open airway.
9. Ensure victim is breathing. Mouth to mouth may be initiated.
10. If upward excursion occurred during the actual convulsion, transport to chamber.

Front 16

What is a successive Oxygen dive?

Back 16

Follows a previous oxygen dive after an Off-Oxygen Interval of less than 2 hours.

Front 17

What are the 3 subsystems of the MK25?

Back 17

Pneumatic
Recirculation
Equipment Case/harness

Front 18

What are the components of the pneumatic subsystem on the MK25?

Back 18

O2 cylinder.
Supply Valve
Oxygen reducer.
Pressure gauge and line (HP).
Connecting line (LP).
Demand valve.
Manual bypass knob.

Front 19

What are the components of the recirculation subsystem on the MK25?

Back 19

Breathing Bag.
Inhalation hose.
Exhalation hose.
Mouthpiece.
Soda lime canister.

Front 20

What is the maximum fill pressure of the O2 cylinder in bar and psig on the MK25?

Back 20

207 bar
3000 psig

Front 21

What is the function of the breathing bag on the MK25?

Back 21

Acts as a flexible gas reservoir and helps provide neutral buoyancy underwater for the UBA.

Front 22

State the differences in appearance between the inhalation and exhalation hoses?

Back 22

Inhalation hose is shorter than the exhalation hose.

Front 23

What are the disadvantages of diving the MK25?

Back 23

Increased hazard to diver (CNS O2 Tox)
Limited to shallow depths.
No voice comms.
Limited thermal protection.
Greater training requirements
Greater expense.

Front 24

What are the advantages of diving MK25?

Back 24

Stealth.
Extended operating duration.
Minimum support.
Portability.
Excellent Mobility.

Front 25

What is the function of the demand valve on the MK25?

Back 25

Adds O2 to the breathing bag as required when the breathing bag is emptied on inhalation.

Front 26

What component allows the diver to manually control O2 supply to the breathing bag in the MK25?

Back 26

Manual by-pass valve.

Front 27

What are the functions of the Soda Lime canister on the MK25?

Back 27

Removes both moisture and CO2 from the gas in the breathing loop.

Front 28

What is the only authorized Oxygne allowed for use when diving the MK25?

Back 28

99.5% pure Aviator O2.

Front 29

How much water can the moisture trap hold before any water should enter the absorbent material?

Back 29

200cc

Front 30

What is the function of the spring inside of the breathing bag?

Back 30

Keeps the breathing bag from collapsing on itself.

Front 31

What is the maximum depth the Secumar TSK 2/42 life vest is authorized to?

Back 31

50 fsw

Front 32

What are the 3 functions of the multipurpose valve (MPV) on the Secumar life preserver?

Back 32

Oral inflation.
Manual deflation.
Over-pressurization.

Front 33

What is the right side air cylinder used for on the Secumar life preserver?

Back 33

only for emergency ascent purposes.

Front 34

What is the left side air cylinder used for on the Secumar life preserver?

Back 34

Buoyancy control in extreme circumstances.

Front 35

What is the maximum and minimum pressures for the Secumar air cylinders?

Back 35

Max- 3000 psi
Min- 2400 psi

Front 36

How many and what size are the air bottles on the Secumar life preserver?

Back 36

2- air cylinders
42 liters

Front 37

What are the normal and maximum working limits for the MK25?

Back 37

Normal: 25 fsw for 240 min.
Max: 50 fsw for 10 min.

Front 38

What is Middle Ear Oxygen Absorption Syndrome?

Back 38

Negative pressure that may develop in the middle ear following a long oxygen dive.

Front 39

What are the symptoms of Middle Ear Oxygen Absorption Syndrom?

Back 39

Sense of pressure or mild discomfort in one or both ears.
Muffled hearing in one or both ears.
Moist, crackling sensation in one or both ears as a result of fluid accumulation in the middle ear.

Front 40

What is canister duration dependent on when diving the MK25?

Back 40

Water temperature.
Exercise rate.
Mesh size of absorbent.

Front 41

Why is it important to ensure proper packing of the CO2 canister?

Back 41

Proper packing minimizes the possibility of channeling. Channeling allows the divers exhaled CO2 to pass through channels in the absorbent material without being absorbed.

Front 42

How many excursions are allowed during a Transit with Excursion dive in the MK25?

Back 42

Only a single excursion is allowed.

Front 43

What are the Single-Depth Oxygen Exposure Limits?

Back 43

25 fsw - 240 min
30 fsw - 80 min
35 fsw - 25 min
40 fsw - 15 min
50 fsw - 10 min

Front 44

How much oxygen time is allowed in a 24 hour period?

Back 44

Maximum of 4 hours oxygen time is permitted within a 24 hour period.

Front 45

How can you maximize operational range in the MK25?

Back 45

Turtleback technique.
Use tides and currents. Avoid swimming against a current if possible.
Oxygen bottles are fully charged before dive.
Minimize gas loss by avoiding leaks and unnecessary depth changes.
Maintain comfortable, rlaxed swim pace.
Wear adequate thermal protection.

Front 46

When are bubby lines required for MK25 diving?

Back 46

Buddy lines are required equipment for oxygen dives. The diving supervisor must carefully consider each situation and allow buddy lines to be disconnected only when their use will impede the performance of the mission.