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98 Cards in this Set

  • Front
  • Back
The MK16 MOD 0 is a ______ ata constant partial pressure of O2 (ppO2) closed-circuit mixed-gas underwater breathing apparatus (UBA) primarily employed by Naval Special Warfare (SPECWAR) forces.
0.75 ata
What is the normal working limit for the MK16 MOD 1 UBA when N2O2 (air) is used as a diluent?
150’
What is the normal working limit for the MK16 MOD 1 UBA when 88/12 HeO2 mix is used as a diluent?
300’
What is the maximum working limit for the MK16 MOD 1 UBA when N2O2 (air) is used as a diluent?
190’
What is the maximum working limit for the MK16 MOD 1 UBA when 88/12 HeO2 mix is used as a diluent?
300’
Due to the increased breathing resistance, and concerns about carbon dioxide retention and CNS O2 toxicity, planned N2O2 dives deeper than ________ fsw are considered exceptional exposure dives and require whos prior approval?
150’, CNO approval
What are the permissible 1.3 ata N2O2 dive profiles?
1. Multiple repetitive dives from 0’–150’ provided all the dives are no-decompression dives.
2. One decompression dive from 0’–150’ plus up to three additional no-decompression dives from 0’–150’. The three no-decompression dives may precede, follow, or bracket the decompression dive.
3. Two decompression dives (initial decompression dive plus one repetitive decompression dive) from 0’–150’. Additional no-decompression dives are not allowed before or after the decompression dives.
4. Repetitive dives from 151’–190’ under the rules above providing CNO grants a waiver for exceptional exposure diving
What are the permissible 1.3 ata HEO2 dive profiles?
1. Multiple repetitive dives from 0’–200’ provided all the dives are no-decompression dives.
2. One decompression dive from 0’–200’ plus up to three additional no-decompression dives from 0’–200’. The three no-decompression dives may precede, follow, or bracket the decompression dive.
3. Two decompression dives (initial decompression dive plus one repetitive decompression dive) from 0’–200’. Additional no-decompression dives are not allowed before or after the decompression dives.
4. One no-decompression dive or one decompression dive from 201–300 fsw. Repetitive diving is not allowed deeper than 200 fsw.

Switching diluents between dives IS OR IS NOT authorized in the MK 16 MOD 1?

Is not authorized. There are no procedures for performing a repetitive dive on helium following a dive on nitrogen or for performing a repetitive dive on nitrogen following a dive on helium
Work up dives are strongly recommended prior to diving at depths greater than _____ fsw.
130’
What are the requirements for a diver who has not made a MK 16 MOD 1 dive in the previous six months prior to making a MK 16 MOD 1 operational dive?
He must refamiliarize himself with MK 16 MOD 1 EPs and OPs and must complete a MK 16 MOD 1 training dive
What are the requirements for a diver a diver who has not conducted a MK 16 MOD 1 decompression dive within the previous six months prior to making a MK-16 MOD 1 decompression dive?
He must complete open water decompression training dives
What is the minimum manning requirements for a MK-16 MOD 1 dive?
4 (one diver) Dive sup, Diver, Standby diver, Diver tender (dive sup may act as logs and standby tender)

One tender per diver when divers are surface tended. If using a buddy line, one tender is required for each buddy pair.
EBS Operator is required for MK 16 MOD 1 decompression dives
What is the purpose of the diluent gas?
Diluent gas is used to maintain the required gas volume in the breathing loop and is not depleted by metabolic consumption. As the diver descends, diluent is added to maintain the total pressure within the recirculation system at ambient water pressure. Loss of UBA gas due to off gassing at depth requires the addition of diluent gas to the breathing loop either automatically through the diluent addition valve or manually through the diluent bypass valve to make up lost volume.
What will rapidly deplete the diluents gas supply?
Excessive gas loss caused by face mask leaks, frequent depth changes, or improper UBA assembly
True or False. A minimum of one motorized safety boat must be present for all open-water dives. A safety boat is also recommended for tended pier dives or diving from shore.
True
Buddy lines are considered important safety equipment for closed-circuit UBA dives. When may the Diving Supervisor shall conduct dives without buddy lines?
Only in situations where their use is not feasible or where their use will pose a greater hazard to the divers than diving without them.
Any buddy line over ______ feet (3 meters) in length is referred to as a distance line.
10‘ The length of the distance line shall not exceed _____ feet (25 meters).
How are lines used for controlling the depth of the diver(s) for decompression diving marked?
Lines shall be marked with red and yellow or black bands starting at the diver(s) or clump end. Red bands will indicate 50’ and yellow or black bands will mark every 10’.
True or False: A single depth gauge and wrist watch may be used when diving with a partner and using a distance line.
True
What visual warning of excess CO2 problems are provided by the MK 16 MOD 0 UBA?
None
The MK 16 MOD 1 UBA is broken down into what four basic systems?
Housing, recirculation, pneumatics, and electronics
The CO2 scrubber assembly performs what two functions?
Carbon dioxide removal and water removal
The partial pressure of O2 within the recirculation system is monitored by how many sensors?
Three
What is the normal operational ppO2 setpoint for the MK 16 Mod 1 UBA?
1.3 ata
What type of displays are in the primary display housing?
Two light-emitting diodes (LEDs). The two LEDs (one red and one green) powered by the primary electronics assembly battery.
The MK 16 MOD 1 secondary display is designed to provide what information?
The condition of the breathing medium, the primary battery voltage and the condition of the secondary batteries. It also serves as a backup for the primary display in the event of a failure or malfunction to the primary electronics assembly, the primary display, or the primary battery. The secondary display functions concurrently with, but independently of, the primary display and displays the O2 sensor readings and primary battery information in digital form.
What are the following indications on the primary display?

1. Steady green:
Normal O2 range, 0.60 to 0.90 ata ppO2 (using a set point of 0.75 ata).
What are the following indications on the primary display?
2. Steady red or simultaneously illuminated steady red and green:
Primary electronics failure.
What are the following indications on the primary display?
3. Flashing green
High O2 content, greater than 0.90 ata ppO2.
What are the following indications on the primary display?
4. Flashing red:
Low O2 content, less than 0.60 ata ppO2.
What are the following indications on the primary display?
5. Alternating red/green:
Normal transition period (ppO2 is transitioning from normal to low, from low to normal, from normal to high, or from high to normal), one sensor out of limits, low primary battery power (displayed on secondary display) or primary electronics failure.
What are the following indications on the primary display?
6. No display (display blanked):
Electronics assembly or primary battery failure
How many and what type of batteries power the secondary display?
Four 1.5-volt batteries for illumination of the LED display only. It does not rely on the primary electronics subassembly, but receives signals directly from the O2 sensors and the primary battery. It will continue to function in the event of a primary electronics assembly failure.
True or False: The minimum personnel requirements for MK 16 MOD 1 diving operations are the same as open circuit SCUBA.
True
In calculating the endurance of the MK 16 MOD 1, the volume and pressures of which flask are used?
Only the O2 flask is considered
How much reserve pressure in the O2 flask is required to drive the reducer?
500 psig
For dive planning purposes, O2 consumption by the diver is computed as _______ scfm (1.4 lpm). This is a conservative value for a diver swimming at 0.85 knots.
0.049 scfm
Under normal conditions the anticipated duration of the MK 16 MOD 1 diluent flask, will or will not exceed that of the O2 flask.
Will exceed
CO2 canister duration is dependant on what two factors?
Depth and water temperature
What is the minimum number of motorized safety boats that must be present for all open-water MK 16 MOD 1 dives?
One
When appropriate during training and non-influence diving operations, standby diver may use open circuit SCUBA to a maximum depth of ______ fsw.
130’
True or False: A recompression chamber and a Diving Medical Officer are not required on the dive station (on the dive station is defined as at the dive location) as prerequisites for closed-circuit UBA diving operations, unless the dive(s) will exceed the maximum working limit
True
A recompression chamber is required on-site for all MK 16 MOD 1 UBA decompression dives deeper than _____ fsw, regardless of the mission.
200’
When diving on unknown or influence ordnance, what must the standby be equipped with?
Standby diver’s equipment shall be the same type as the diver performing the actual procedure
Who may authorize the employment of a single, untended diver when it is deemed that the ordnance hazard is greater than the hazard presented by diving alone?
The EOD Diving Officer
All single, untended divers shall be equipped with what?
A full face mask (FFM).What is the maximum descent rate for MK 16 MOD 1?
What is the maximum descent rate for MK 16 MOD 1?
60 fpm
How often should the diver monitor primary and secondary displays?
Frequently (every 2-3 minutes)
What should the diver check for while checking the primary display?
That the O2 level remains at the setpoint during normal activity at a constant depth.
What should the diver check for while checking the secondary display?
That all sensors are consistent with the primary display and that plus and minus battery voltages are properly indicating.
During ascent, when water pressure decreases, the diaphragm dump valve compensates for increased gas volume by discharging the excess gas into the water. As a result, O2 in the breathing gas mixture may be vented faster than O2 is replaced by the addition valve. In this case, the primary display may show what lights?
Alternate red/green before the low ppO2 signal (blinking red) appears. This is a normal transition period and shall not cause concern. Monitor the secondary display frequently on ascent and add O2 by depressing the bypass valve during this instance.
During ascent, when water pressure decreases, the ppO2 in the breathing gas mixture may decrease faster than O2 can be added via the O2 addition valve. Under these circumstances, the primary display may show what lights?
Alternate red/green, then flashing red for low ppO2.
Even with strict adherence to an ascent rate of 30 fpm, the diver may experience flashing red on the primary display. This may also be an indication of a rig malfunction. What can the diver do to discriminate between a normal decrease in oxygen partial pressure due to ascent and a UBA malfunction?
Add O2 while observing the secondary display

Other actions the diver may take are:
Upon arrival at the first decompression stop allow the UBA to stabilize. If after four minutes of arrival at the first stop a flashing red persists on the primary display the diver should initiate the appropriate emergency procedure for low ppO2.
There is an increased risk of CNS oxygen toxicity when diving the MK 16 MOD 1 compared to diving the MK 16 MOD 0, especially during the descent phase of the dive. Diving supervisors and divers should be aware that oxygen partial pressures of _____ ata or higher may be temporarily experienced during descent on N2O2 dives deeper than ______ fsw (21% oxygen diluent) and on HeO2 dives deeper than ______ fsw (12% oxygen diluent).
1.6 ata, N2O2 - 120’, HeO2 – 200’
During decompression, it is very important to constantly monitor the secondary display and ensure a 1.3 ppO2 is maintained as closely as possible. What table do you use if a UBA malfunction has significantly altered the ppO2?
Always use the appropriate decompression table when surfacing, even if UBA malfunction has significantly altered the ppO2.
True or False:
Surface decompression is not authorized for MK 16 MOD 1 operations.
True
For HeO2 dives, what must you do after going on gas during the dive supervisor checks?
Flush the UBA well with helium-oxygen using the purge procedure given in the MK 16 MOD 1 O&M manual. (three open circuit breathing cycles)
True or False: The repetitive group designators are not interchangeable between the nitrogen and helium decompression tables. There are no procedures for performing repetitive dives when the inert gas in the diluent mixture changes between dives.
True
True or False: In MK16 MOD 1 diving operations, the maximum ascent rate is 30 feet per minute and the rules for compensating for variations in the rate of ascent are identical to those for air diving.
True
True or False: The rules for compensating for variations in the rate of ascent are identical to those for air diving
True
The MK 16 MOD 1 UBA primary display should indicate a transition from 0.75 to 1.3 ata at _____ fsw. The diver should verify this transition by monitoring his ___________________.
33’ +/- 2’, secondary display
If there is no indication of transition with continued descent past ______ fsw, the dive should be terminated and the diver should ascend to the surface in accordance with the appropriate decompression schedule.
40’
What is the last water stop during decompression?
20’
During ascent to the surface, the primary electronics will switch from 1.3 ata ppO2 to 0.75 ata ppO2 above what depth?
Upon ascent above 13’
What are the divers actions for the following emergency situations: UBA flood-out or failure?
Immediately ascend to the first decompression stop according to the original decompression schedule if deeper than the first stop, and shift to the Emergency Breathing System (EBS).
The partial pressure of inert gas (nitrogen or helium) in the MK 16 MOD 1 UBA at depths down to _____ fsw is lower than the partial pressure of nitrogen in air at the surface.
15’
If a dive is a repetitive dive to 15 fsw or shallower, a diver will lose rather than gain inert gas during the dive. Accordingly, the diver does not acquire a repetitive group designator when making these shallow dives. How do you figure the RNT/RHT for another 3rd dive?
The dive to 15’ or shallower can be considered the equivalent of remaining on the surface for the duration of the dive. The repetitive group designator at the end of the repetitive dive can be determined by adding the bottom time of the 15’ or shallower repetitive dive to the preceding surface interval, then using the RNT/RHT table to determine the ending repetitive group.
True or False: The RNT and RHT exception rules apply to repetitive MK 16 MOD 1 diving.
True, The RNT and RHT exception rules read identically.

During descent, the MK 16 MOD 1 switches from the 0.75 ata mode to the 1.3 ata mode at 33’ ± 2’. The decompression tables assume that the diver is in the 0.75 ata mode up to a depth of 35’.
The RNT and RHT exception rules can be used when all the MK-16 dives in the series are to 35’ and shallower (ppO2 = 0.75 ata) or when all the dives in the series are deeper than 35’ (ppO2 = 1.3 ata). However, when some dives are shallower than 35’ and others are deeper, what special procedure must be used to apply the RNT/RHT exception rule?
The shallow 0.75 ata dives must first be converted to their 1.3 ata equivalent depth before the deepest depth in the series is determined. The equivalent depth on 1.3 ata can be obtained by adding 20’ to the depth of the dive on 0.75 ata.
What are the procedures to perform a repetitive MK-16 MOD 1 N2O2 dive following an air dive?
1. Obtain the repetitive group designator following the air dive from either the air no ‘D’ table or the air decompression table.
2. Using that repetitive group designator, enter the MK-16 N2O2 RNT timetable on the diagonal. Read across the row to the surface interval between the air and MK 16 dive, then down to the depth of the MK 16 dive to obtain the residual nitrogen time.
3. Add the RNT to the bottom time of the repetitive MK-16 dive to obtain the Equivalent Single Dive Time.
4. Enter the MK-16 N2O2 no ‘D’ table or the MK-16 N2O2 decompression table at the depth that is exactly equal to or next deeper than the actual depth of the repetitive dive. Select the schedule that is exactly equal to or next longer than the Equivalent Single Dive Time. Follow the prescribed decompression to the surface.
What are the procedures to apply the RNT/RHT exception rule to a repetitive MK-16 MOD 1 N2O2 dive following an air dive?
If all the MK 16 MOD 1 dives in the series, including the repetitive dive, are to 35’ or shallower, convert the depth(s) of the air dive(s) in the series to the equivalent depth on 0.75 ata before taking the deepest depth in the series.

Equivalent Depth on 0.75 ata = (0.79 x Depth on Air) + 18’.

If any of the MK 16 MOD 1 dives in the series, including the repetitive dive, are to a depth greater than 35’, convert the depth(s) of the air dive(s) in the series to the equivalent depth on 1.3 ata before taking the deepest depth in the series.

Equivalent Depth on 1.3 ata = (0.79 x Depth on Air) + 36’.
The ppO2 in the MK 16 MOD 1 UBA is expected to vary slightly from ____________ ata for irregular brief intervals.
1.15 – 1.45 ata
The Diving Supervisor and medical personnel should recognize that a diver who has been breathing a mixture with ppO2 lower than ______ ata for any length of time may have a greater risk of developing_________________________. Such a diver requires observation after surfacing, but need not be treated unless symptoms of decompression sickness occur.
1.15 ata, decompression sickness
When does the time at the divers first decompression stop begin?
Begin timing the first stop when the diver arrives at the stop
When does the time at the divers decompression stop begin for all subsequent stops after the first stop?
Time begins when the diver leaves the previous stop. Ascent time between stops is included in the subsequent stop time.
When selecting the proper decompression table for repet dives, all dives within the past _____ hours must be considered.
18 hours
Regardless of the depth of the first decompression stop the EBS must be lowered to at least ______ fsw and why?
40’, to allow the hydrostatic switch in the primary electronics to switch from 0.75 ata ppO2 to 1.3 ata ppO2.
After the EBS has been lowered to 40’ it must be raised or lowered to what depth?
10’ below the first decompression stop.
To what depth is it recommended the EBS be kept at during decompression dives?
It is recommended to lower EBS to 50’ if the first decompression stop is shallower than 40’. This allows for topside personnel to track delays in ascent deeper than 50’.
When conducting decompression dives it is highly recommended to utilize what piece of equipment?
Through water communications
Repetitive exposure to an oxygen partial pressure of 1.3 ata over a multi-day period may result in the gradual development of pulmonary oxygen toxicity. The diver may experience burning substernal pain on inspiration, chest tightness, cough, and/or shortness of breath. The diver may also experience a temporary change in visual acuity. Distant objects may appear out of focus. To minimize the possibility of pulmonary or visual oxygen toxicity during multi-day diving with the MK 16 MOD 1, the diver shall adhere to what following?
1. Limit total dive time on the MK 16 MOD 1 to a maximum of 4 hours per day.
2. Limit total dive time on the MK 16 MOD 1 to a maximum of 16 hours per week.
3. Shallow dives in which the rig remains in the 0.75 ata mode throughout are excluded from the above totals.
4. Commanding Officer’s permission is required to exceed these limits.
5. If more dive time is required to accomplish a specific mission, contact NEDU for additional guidance.
6. If symptoms of pulmonary or visual oxygen toxicity develop at any time during a multi-day mission, stop diving until all symptoms have resolved and the diver remains symptom-free for a minimum of 24 hours.
Ascent to altitude following a MK 16 MOD 1 dive at sea level will increase the risk of decompression sickness if the interval on the surface before ascent is not long enough to permit excess nitrogen or helium to be eliminated from the body. What are the procedures to determine the safe surface interval before ascent?
Nitrogen-Oxygen Dives
1. Determine the highest repetitive group designator obtained in the previous 24-hour period.
2. Using the highest repetitive group designator, enter Table 9 6, Required Surface Interval Before Ascent to Altitude After Diving. Read across the row to the altitude that is exactly equal to or next higher than the planned change in altitude to obtain the safe surface interval.
Helium-Oxygen Dives
1. For no-decompression dives with total bottom times, including repetitive dives, less than 2 hours, wait 12 hours on the surface before ascending to altitude.
2. For no-decompression dives with bottom times, including repetitive dives, greater than 2 hours or for decompression dives, wait 24 hours on the surface before ascending to altitude.
The MK 16 MOD 1 decompression procedures may be used for diving at altitudes up to ______ feet without modification. Who do you contact for guidance for any planned dives at altitudes above this level?
1000’, NAVSEA 00C
What must the diver do when high levels of O2 are displayed during descent?
Though the MK 16 MOD 1 UBA maintains a ppO2 of approximately 1.3 ata, a rapid descent may not allow the oxygen already in the circuit to be consumed fast enough resulting in a high ppO2. When high levels of oxygen are displayed, the descent must be slowed.
If the diver is in less than ______ fsw, little danger of oxygen toxicity exists.
20’
If the diver is deeper than _____ fsw, and a ppO2 of _______ ata or higher persists within the UBA for a period of ______ consecutive minutes this condition should be treated as a malfunction of the UBA and the appropriate emergency procedures should be followed.
20’, ppO2 1.45 ata, :15
If non-convulsive symptoms of CNS O2 toxicity occur, what action must be taken immediately to lower the O2 partial pressure by the diver?
1. Ascend. Dalton’s law will lower the O2 partial pressure.
2. Add diluent to the breathing loop.
3. Secure the O2 cylinder if O2 addition is uncontrolled.
Though an ascent from depth will lower the partial pressure of O2, the diver may still suffer other or worsening symptoms. The divers should notify the Diving Supervisor and terminate the dive.
What actions should be taken when treating a convulsing diver in the water?
1. Assume a position behind the convulsing diver. Release the victim’s weight belt only if progress to the surface is significantly impeded.
2. Do not ascend in the water until the convulsion subsides.
3. Open the victim’s airway and leave the mouthpiece in his mouth. If it is not in his mouth, do not attempt to replace it; however, ensure that the mouthpiece is switched to the SURFACE POSITION to prevent unnecessary negative buoyancy from a flooded UBA.
4. Grasp the victim around his chest above the UBA or between the UBA and his body. If difficulty is encountered in gaining control of the victim in this manner, the rescuer should use the best method possible to obtain control.
5. Ventilate the UBA with diluent to lower the ppO2 and maintain depth until the convulsion subsides.
6. Make a controlled ascent to the first decompression stop, maintaining a slight pressure on the diver’s chest to assist exhalation.
a. If the diver regains control, continue with appropriate decompression.
b. If the diver remains incapacitated, surface at a moderate rate, establish an airway, and treat for symptomatic omitted decompression.
c. Frequent monitoring of the primary and secondary displays as well as the O2- and diluent-bottle pressure gauges will keep the diver well informed of his breathing gas and rig status.
7. If additional buoyancy is required, activate the victim’s life jacket. The rescuer should not release his own weight belt or inflate his life jacket.
8. Upon reaching the surface, inflate the victim’s life jacket if not previously done.
9. Remove the victim’s mouthpiece and switch the valve to SURFACE to prevent the possibility of the rig flooding and weighing down the victim.
10. Signal for emergency pickup.
11. Ensure the victim is breathing. Mouth-to-mouth breathing may be initiated if necessary.
12. If an upward excursion occurred during the actual convulsion, transport to the nearest chamber and have the victim evaluated by an individual trained to recognize and treat diving-related illness.
What is the primary cause of hypoxia for a MK16 diver?
The failure of the O2 addition valve or primary electronics. Depletion of the O2 supply or malfunctioning O2 sensors can also lead to a hypoxic gas mixture.
During a rapid ascent Dalton’s law may cause the ppO2 to fall faster than can be compensated for by the O2-addition system. What are your actions if, during ascent, low levels of O2 are displayed?
Slow the ascent and add O2 if necessary.
If symptoms of hypoxia develop, the diver must take immediate action to raise the O2 partial pressure. If unconsciousness occurs, what actions should the buddy diver take if the diver does not require decompression?
Add oxygen to the rig while monitoring the secondary display. If the diver does not require decompression, the buddy diver should bring the afflicted diver to the surface at a moderate rate, remove the mouthpiece or mask, and have him breathe air. If the event was clearly related to hypoxia and the diver recovers fully with normal neurological function shortly after breathing surface air, the diver does not require treatment for arterial gas embolism.
If symptoms of hypoxia develop, the diver must take immediate action to raise the O2 partial pressure. If unconsciousness occurs, what actions should the buddy diver take if the diver does not require decompression?
The buddy diver should bring the afflicted diver to the first decompression stop.
1. If consciousness is regained, continue with normal decompression.
2. If consciousness is not regained, ascend to the surface at a moderate rate (not to exceed 30 fpm), establish an airway, administer 100 % O2, and treat for symptomatic omitted decompression. If possible, immediate assistance from the standby diver should be obtained and the unaffected diver should continue normal decompression.
What are the causes of Hypercapnia in a MK-16 diver?
It is generally a result of the failure of the carbon dioxide-absorbent material. The failure may be a result of channeling, flooding or saturation of the absorbent material. Skip breathing or controlled ventilation by the diver, which results in an insufficient removal of CO2 from the diver’s body, may also cause hypercapnia.
If symptoms of hypercapnia develop, what actions should the diver take?
1. Immediately stop work and take several deep breaths.
2. Increase ventilation if skip-breathing is a possible cause.
3. Ascend. This will reduce the partial pressure of carbon dioxide both in the rig and the lungs.
4. If symptoms do not rapidly abate, the diver should abort the dive.
5. During ascent, while maintaining a vertical position, the diver should activate his bypass valve, adding fresh gas to his UBA. If the symptoms are a result of canister floodout, an upright position decreases the likelihood that the diver will sustain chemical injury.
6. If unconsciousness occurs at depth, the same principles of management for underwater convulsion apply.
What are some ways to minimize the risk of hypercapnia?
1. Use only an approved carbon dioxide absorbent in the UBA canister.
2. Follow the prescribed canister-filling procedure to ensure that the canister is correctly packed with carbon dioxide absorbent.
3. Dip test the UBA carefully before the dive. Watch for leaks that may result in canister floodout.
4. Do not exceed canister duration limits for the water temperature.
5. Ensure that the one-way valves in the supply and exhaust hoses are installed and working properly.
6. Swim at a relaxed, comfortable pace.
7. Avoid skip-breathing. There is no advantage to this type of breathing in a closed-circuit rig and it may cause elevated blood carbon dioxide levels even with a properly functioning canister.
What causes a “caustic cocktail” in a MK-16?
A caustic alkaline solution results when water leaking into the canister comes in contact with the carbon dioxide absorbent. The water may enter through a leak in the breathing loop or incorrect position of the mouthpiece rotary valve during a leak check. When the diver is in a horizontal or head down position, this solution may travel through the inhalation hose and irritate or injure the upper airway.
What are the symptoms of a “caustic cocktail” in a MK-16?
Before actually inhaling the caustic solution, the diver may experience labored breathing or headache, which are symptoms of carbon dioxide buildup in the breathing gas. This occurs because an accumulation of the caustic solution in the canister may be impairing carbon dioxide absorption. If the problem is not corrected promptly, the alkaline solution may travel into the breathing hoses and consequently be inhaled or swallowed. Choking, gagging, foul taste, and burning of the mouth and throat may begin immediately. This condition is sometimes referred to as a “caustic cocktail.” The extent of the injury depends on the amount and distribution of the solution.
What actions are taken for a diver suffering from a “caustic cocktail”?
If the caustic solution enters the mouth, nose, or face mask, the diver must take the following steps:
1. Immediately assume an upright position in the water.
2. Depress the manual diluent bypass valve continuously.
3. If the dive is a no-decompression dive, make a controlled ascent to the surface, exhaling through the nose to prevent overpressurization.
4. If the dive requires decompression, shift to the EBS or another alternative breathing supply. If it is not possible to complete the planned decompression, surface the diver and treat for omitted decompression.

Using fresh water, rinse the mouth several times. Several mouthfuls should then be swallowed. If only sea water is available, rinse the mouth but do not swallow. Other fluids may be substituted if available, but the use of weak acid solutions (vinegar or lemon juice) is not recommended. Do not attempt to induce vomiting.
A chemical injury may cause the diver to have difficulty breathing properly on ascent. He should be observed for signs of an arterial gas embolism and should be treated if necessary. A victim of a chemical injury should be evaluated by a physician or corpsman as soon as possible. Respiratory distress which may result from the chemical trauma to the air passages requires immediate hospitalization.