CHAPTER 14 — Surface-Supplied Mixed-Gas Diving Procedures 14-1
CHAPTER 14
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14-1
INTRODUCTION
14-1.1
Purpose.
The purpose of this chapter is to familiarize divers with U.S. Navy
surface-supplied procedures.
14-1.2
Scope.
Surface-supplied mixed-gas diving is conducted with helium-oxygen
mixtures supplied from the surface by a flexible hose. Surface-supplied mixed-gas
diving is particularly suited for operations beyond the depth limits of air diving,
yet short of the depths and times requiring the use of a deep diving system.
Surface-supplied mixed-gas diving is also useful in the deep air diving range when
freedom from nitrogen narcosis is required.
14-2
PLANNING THE OPERATION
Planning surface-supplied mixed-gas dives involves many of the same consider-
ations used when planning an air dive. Planning aspects that are unique to surface-
supplied mixed-gas diving include the logistics of providing several different gas
mixtures to the diver and the limitations on the duration of carbon dioxide absorp-
tion canisters in cold water.
14-2.1
Depth and Exposure Time.
The normal operational limit for surface-supplied
mixed-gas diving is 300 fsw. Within each decompression table (Table 14-7),
exceptional-exposure dives are enclosed in red boxes to separate them from
normal working dives. Exceptional-exposure dives require lengthy decompression
and are associated with an increased risk of decompression sickness and exposure
to the elements. Exceptional exposures should be undertaken only in emergency
circumstances. Planned exceptional-exposure dives require prior CNO approval.
Repetitive diving is not allowed in surface-supplied helium-oxygen diving.
14-2.2
Water Temperature.
Loss of body temperature (hypothermia) can be a major
problem during long, deep dives. Because the high thermal conductivity of helium
in a dry suit accelerates the loss of body heat, a hot water suit is preferred for
surface-supplied dives when using the MK 21 MOD 1 in very cold water.
Refer to Chapter 3 for more information on thermal problems and the signs and
symptoms of hypothermia. Refer to Chapter 11 for information on ice and cold
water diving operations.
14-2.3
Gas Mixtures.
Air, 100 percent oxygen, and several helium-oxygen mixtures will
be required to dive the surface-supplied mixed-gas tables over their full range. The
logistics of supplying these gases must be carefully planned. Analysis of the
14-2 U.S. Navy Diving Manual—Volume 3
oxygen content of helium-oxygen mixtures shall be accurate to within ±0.5
percent.
14-2.3.1
Maximum/Minimum Mixtures.
For each depth in the decompression tables, the
allowable maximum and minimum oxygen percentage in the helium-oxygen
mixture used on the bottom is specified. For operations planning, the range of
possible depths should be established and a mixture selected that will meet the
maximum/minimum specification across the depth range. The maximum oxygen
concentration has been selected so that the diver never exceeds an oxygen partial
pressure of 1.3 ata while on the bottom. The minimum oxygen percentage allowed
in the mixture is 16 percent for depths to 200 fsw, 12 percent for depths from 200
fsw to 300 fsw, and 10 percent for depths in excess of 300 fsw. Diving with a
mixture near maximum oxygen percentage is encouraged as it offers a decompres-
sion advantage to the diver.
14-2.3.1.1
On the Surface.
On the surface, the diver’s gas mixture must contain a minimum
of 16 percent oxygen. When a bottom mix with less than 16 percent oxygen is to
be used, a shift to the bottom mix is made at 20 fsw during descent (see paragraph
14-3.2).
14-2.3.1.2
Deeper than 200 fsw.
For dives deeper than 200 fsw in which the bottom mixture
contains less than 16 percent oxygen, a gas shift from the bottom mix to a 60
percent helium/40 percent oxygen mixture is required at the 100-fsw decompres-
sion stop or the next shallower stop if there is no 100-fsw stop (see paragraph
14-3.3).
14-2.3.1.3
Up to 200 fsw.
For dives to 200 fsw and shallower or for deeper dives in which
the bottom mixture contains more than 16 percent oxygen, a shift to 60 percent
helium/40 percent oxygen is not required but can be executed to increase decom-
pression safety if desired.
14-2.3.1.4
Exceptional Exposure Dives.
For exceptional-exposure dives, a shift to a 60
percent helium/40 percent oxygen mixture is required at the 100-fsw stop or the
next shallower stop if there is no 100-fsw stop.
On all dives, a shift to 100 percent oxygen is made at the 50-fsw or 40-fsw water
stop if there is no 50-fsw stop.
14-2.3.2
Emergency Gas Supply.
All divers are equipped with an emergency gas supply
(EGS). The EGS gas mixture will be the same as the bottom mixture unless the
bottom mixture contains less than 16 percent oxygen, in which case the EGS gas
mixture will be 16 + 0.5 percent oxygen and the balance will be helium. The EGS
bottle shall be a minimum of 64.7 (steel 72) cubic feet charged to 1,800 psi.
14-3
SURFACE-SUPPLIED HELIUM-OXYGEN DESCENT AND ASCENT PROCEDURES
The Surface-Supplied Helium-Oxygen Decompression Table (Table 14-7) is used
to decompress divers from surface-supplied helium-oxygen dives. The table is in a
depth-time format similar to the U.S. Navy Air Decompression Table and is used
CHAPTER 14 — Surface-Supplied Mixed-Gas Diving Procedures 14-3
in a similar fashion. One additional table, the Emergency Procedures Decompres-
sion Table (Table 14-1), is used under emergency conditions (see paragraph
14-4.4).
14-3.1
Surface-Supplied Helium-Oxygen Decompression Table.
The Surface-Supplied
Helium-Oxygen Decompression Table (Table 14-7) specifies the maximum and
minimum concentrations of oxygen allowable in the helium-oxygen mixture at
depth. Select a gas mixture for the dive that is compatible with the deepest depth
anticipated for the dive.
14-3.1.1
Calculating Maximum Depth.
To select the proper decompression table and
schedule, measure the deepest depth reached by the diver and enter the table at the
exact or next greater depth. When using an air-filled pneumofathometer to
measure depth, the observed depth reading must be corrected as shown in Table
14-2. It is also important that the pneumofathometer be at mid-chest level. Enter
the table at the maximum or next greater depth. It is also important that the pneu-
mofathometer be at mid-chest level. The bottom time is measured as the time from
leaving the surface to leaving the bottom, rounded up to the next whole minute,
except as noted in paragraph 14-3.2. Enter the table at the exact or next greater
bottom time.
Example.
The divers pneumofathometer reads 250 fsw. In the depth range of
201-300 fsw, the pneumofathometer underestimates the divers true depth by 4
Table 14-1. Emergency Procedures Decompression Table.
Decompression Stop Depth (fsw) Decompression Stop Time (min)
50 30
40 35
30 42
20 52
10 68
Table 14-2. Pneumofathometer Correction Factors.
Pneuofathometer Depth Correction Factor
0-100 fsw +1 fsw
101-200 +2 fsw
201-300 +4 fsw
301-400 +7 fsw
14-4 U.S. Navy Diving Manual—Volume 3
fsw. To determine the true depth, 4 fsw must be added to the pnuemofathometer
reading. The divers true depth is 254 fsw.
14-3.1.2
Travel Rates.
The descent rate is not critical, but it should not exceed 75 fsw/min.
The ascent rate is at a constant rate of 30 fsw/minute. The ascent time between
stops is included in the time of the subsequent stop, except when reaching the first
stop and when the shift to 100 percent oxygen is made.
14-3.1.3
Decompression Breathing Gas.
For dives as deep as 200 fsw, decompression is
taken on the bottom mixture up to the 50-fsw water stop (40-fsw if 40 fsw is the
first stop) and the diver is then shifted to 100 percent oxygen. For dives greater
than 200 fsw, decompression is taken on the bottom mixture to the 100-fsw water
stop (or next shallower stop if there is no 100-fsw stop) and the diver is then
shifted to a 60 percent helium/40 percent oxygen mixture. Upon arrival at the 50-
fsw water stop, the diver is shifted to 100 percent oxygen. Surface decompression
may be taken after completing a portion of the 40-fsw oxygen stop on all dives, as
described in paragraphs 14-3.7 and 14-3.8.
14-3.2
Special Procedures for Descent with Less than 16 percent Oxygen.
14-3.2.1
Descent Procedure.
To prevent hypoxia, a special descent procedure is required
when the bottom mixture contains less than 16 percent oxygen:
1.
Place the diver on the surface on air.
2.
Make the appropriate predive checks.
3.
Have the diver descend to 20 fsw.
4.
At 20 fsw, shift the diver to the bottom mix and ventilate. The diver is allowed
10 minutes at 20 fsw to shift to the bottom mixture and perform equipment
checks.
5.
Confirm the diver is on bottom mix, then perform a final leak check.
6.
Have the diver begin descent. On the diving chart, note the time from leaving
the surface to leaving 20 fsw in case the dive must be aborted during descent.
7.
Start counting bottom time:
If the diver spends 10 minutes or less at 20 fsw, bottom time starts when the
diver leaves 20 fsw.
If the diver spends more than 10 minutes at 20 fsw, bottom time starts at the
10-minute mark.
14-3.2.2
Aborting the Dive.
If it is necessary to bring the diver back to the surface from 20
fsw:
1.
Shift the diver from the bottom mixture to air.
CHAPTER 14 — Surface-Supplied Mixed-Gas Diving Procedures 14-5
2.
Ventilate the diver.
3.
Confirm the diver is on air.
4.
Have the diver begin ascent.
5.
When the diver reenters the water the 10-minute period begins again.
14-3.3
Procedures for Shifting to 60 Percent Helium/40 Percent Oxygen at 100 fsw.
For dives deeper than 200 fsw in which the bottom mixture contains less than 16
percent oxygen, it is necessary to shift from the bottom mixture to 60 percent
helium/40 percent oxygen at 100 fsw during decompression or the next shallower
stop if there is no 100-fsw decompression stop. Ventilate each MK 21 MOD 1
diver using the following procedures.
1.
Ventilate each diver and listen for the gas-flow change over the communica-
tions.
2.
Once a gas-flow change is heard, continue to vent for an additional 10 sec-
onds. If a gas-flow change cannot be heard, ventilate for a minimum of 20
seconds.
The time required to effect the shift over to 40 percent oxygen is not critical.
14-3.4
Procedures for Shifting to 100 Percent Oxygen at the First Oxygen Stop.
All
dives except no-decompression dives require a shift to 100 percent oxygen at the
50-fsw stop, or at the 40-fsw stop if there is no 50-fsw stop. Upon arrival at the
stop, ventilate each MK 21 MOD 1 diver with oxygen following these steps:
1.
Ventilate each diver and listen for the gas-flow change over the communica-
tions.
2.
Once a gas-flow change is heard, continue to vent for an additional 10 sec-
onds. If a gas-flow change cannot be heard, ventilate for a minimum of 20
seconds.
Verify the divers voice change. Time at the stop begins when the diver is
confirmed to be on oxygen. When 50 fsw is the first oxygen stop, the ascent time
from 50 fsw to 40 fsw is included in the time of the 40-fsw stop.
14-3.5
Ascent from the 40-fsw Water Stop.
For normal in-water decompression, the
diver surfaces from 40 fsw during the last minute of the 40-fsw stop. Ascent rate is
40 fsw/min. For example, if the 40-fsw stop is 68 minutes, the diver remains at 40
fsw for 67 minutes. During the last minute, he travels to the surface at 40 fsw/
minute. Figure 14-1 shows the diving chart for this dive; the in-water decompres-
sion dive profile is shown in Figure 14-2.
14-3.6
Surface Decompression Procedures (SUR D).
There are two types of surface
decompression procedures, Normal SUR D and Emergency SUR D. Normal SUR
14-6 U.S. Navy Diving Manual—Volume 3
Figure 14-1.
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Diving Chart.
CHAPTER 14 — Surface-Supplied Mixed-Gas Diving Procedures 14-7
Figure 14-2.
In-Water Decompression Dive Profile for a 249 fsw/:18 Dive.
14-8 U.S. Navy Diving Manual—Volume 3
D procedures are preferred over in-water decompression procedures in routine
operations. Normal SUR D procedures improve the divers comfort and safety but
increase total decompression time and oxygen consumption. Emergency SUR Ds
are used for handling CNS oxygen toxicity symptoms, systems failures and other
emergency conditions. Emergency surface decompression allows the diver to be
removed from the water in the shortest possible time.
14-3.7
Normal SUR D Procedures Using Oxygen.
A diver is eligible for normal surface
decompression if he has been on oxygen at 40 fsw for a length of time equal to that
of the 50-fsw stop. If there is no 50-fsw stop, 10 minutes on oxygen at 40 fsw is
required.
Example.
If the 50-fsw stop time is 12 minutes, the diver must remain on oxygen
at 40 fsw for 12 minutes before normal surface decompression can be
implemented.
14-3.7.1
Initiating Normal Surface Decompression.
To initiate normal surface decom-
pression:
1.
Bring the diver to the surface at 40 fsw/min and undress him.
2.
Place the diver in the recompression chamber.
3.
Compress on air to 40 fsw at a maximum compression rate of 80 fsw/min and
place the diver on 100 percent oxygen by mask. The interval from leaving 40
fsw in the water to arriving at 40 fsw in the chamber cannot exceed 5 minutes.
4.
At 40 fsw in the chamber, the diver breathes oxygen for 30-minute periods
separated by 5-minute air breaks. The number of oxygen periods required
depends on the time of the 40-fsw water stop as indicated in Table 14-3.
5.
When the last oxygen breathing period has been completed, return the diver to
breathing chamber air.
6.
Ascend to the surface from 40 fsw in the chamber at a rate of 30 feet per
minute.
A normal surface decompression dive chart is shown in Figure 14-3. A normal
surface decompression dive profile is shown in Figure 14-4.
Table 14-3. Recompression Chamber Breathing Requirements.
Water Stop Oxygen Breathing Period(s)
30 minutes or less 1 period
31–60 minutes 2 periods
61–90 minutes 3 periods
Greater than 90 minutes 4 periods
CHAPTER 14 — Surface-Supplied Mixed-Gas Diving Procedures 14-9
Figure 14-3.
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Diving Chart.
14-10 U.S. Navy Diving Manual—Volume 3
Figure 14-4.
Normal Surface Decompression Dive Profile for a 249 fsw/:18 Dive.
CHAPTER 14 — Surface-Supplied Mixed-Gas Diving Procedures 14-11
14-3.8
Emergency SUR D Procedures Using Oxygen.
A diver is eligible for emergency
surface decompression if he is on oxygen at the 40-fsw water stop and is within 5
minutes of repeating the 50-fsw stop time. If there is no 50-fsw stop, 5 minutes on
oxygen at 40 fsw is required.
Example.
If the 50-fsw stop time is 12 minutes, the diver must remain at 40 fsw
breathing oxygen for 7 minutes before emergency surface decompression can be
initiated.
The emergency surface decompression procedure is identical to the normal
surface decompression procedure except that the length of the first oxygen
breathing period at 40 fsw in the recompression chamber is lengthened from 30
minutes to 40 minutes. An emergency surface decompression dive chart is shown
Figure 14-5; the profile is shown in Figure 14-6.
14-3.9
Aborted Dive During Descent.
Follow these procedures when a dive must be
aborted during descent.
14-3.9.1
Dive Aborted at 200 fsw or Shallower.
Add any time spent shifting gases at 20 fsw to the bottom time to derive a
corrected bottom time.
Enter the table at the deepest depth attained by the diver and select the
schedule corresponding to the corrected bottom time.
Decompress according to the indicated schedule.
14-3.9.2
Dive Aborted Deeper than 200 fsw.
No correction of the bottom time for time spent at 20 fsw is needed.
Enter the table at the deepest depth attained by the diver and select the
schedule corresponding to the bottom time.
Decompress according to the indicated schedule.
14-3.9.3
No-Decompression Limits.
In many instances the diver will be observed to fall
within the no-decompression limits when the above procedures are followed.
If the diver falls within the no-decompression limits and is breathing at least
16 percent oxygen, surface the diver at 30 fsw/minute.
If the diver falls within the no-decompression limits but is breathing less than
16 percent oxygen:
1.
Bring the diver to 20 fsw at 30 fsw/minute.
2.
Shift the diver to air and ventilate.
14-12 U.S. Navy Diving Manual—Volume 3
Figure 14-5.
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Diving Chart.
CHAPTER 14 — Surface-Supplied Mixed-Gas Diving Procedures 14-13
Figure 14-6.
Emergency Surface Decompression Dive Profile for a 249 fsw/:18 Dive.
14-14 U.S. Navy Diving Manual—Volume 3
3.
Surface the diver from 20 fsw when it is confirmed that the diver is breath-
ing air.
Example.
A diver intends to dive to 300 fsw. Five minutes is spent at 20 fsw
shifting from air to an 88 percent helium/12 percent oxygen mixture. Descent is
then begun at 60 fsw/min, but at 80 fsw the diver signals for a hold because he is
unable to clear. After 2 minutes at 80 fsw, the dive is aborted. The bottom time is
3 minutes: 1 minute for the descent and 2 minutes at 80 fsw. The corrected bottom
time is 8 minutes: 5 minutes at 20 fsw and 3 minutes of bottom time. The table
shows an 80 fsw dive for 8 minutes is well within the no-decompression limit of
25 minutes. The diver should ascend to 20 fsw at 30 fsw/min, shift to air, ventilate,
and then ascend directly to the surface.
Example.
A diver intends to dive to 200 fsw on an 84 percent helium/16 percent
oxygen mixture. The diver descends from the surface to 60 fsw at 60 fsw/min. No
time is spent at 20 fsw shifting gases. At 60 fsw the diver signals for a hold and
after 3 minutes at 60 fsw, the dive is aborted. The bottom time and the corrected
bottom time are both 4 minutes: zero minutes at 20 fsw, 1 minute for descent, and
3 minutes at depth. The table shows a 60 fsw dive for 4 minutes is well within the
no-decompression limit of 40 minutes. This diver may ascend directly to the
surface at 30 fsw/min.
Example.
A diver intends to dive to 300 fsw. Eight minutes is spent at 20 fsw
shifting from air to an 88 percent helium/12 percent oxygen mixture. Descent is
begun at 60 fsw/min but at 140 fsw the diver signals for a hold. After 2 minutes at
140 fsw the dive is aborted. The corrected bottom time is 12 minutes: 8 minutes at
20 fsw, 2 minutes of descent time from 20 fsw to 140 fsw and 2 minutes at 140
fsw. Decompression would take place on the 140-fsw/20-minute schedule.
14-3.10
Variation in Rate of Ascent.
The rate of ascent to the first stop and between
subsequent stops is 30 fsw/minute. Minor variations in the rate of travel between
20 and 40 fsw/minute are acceptable.
14-3.10.1
Early Arrival at the First Stop.
If the divers arrive early at the first stop:
1.
Begin timing the first stop when the required travel time has been completed.
2.
If the first stop is 50 or 40 fsw and arrival at the stop is early, shift to oxygen
and begin stop time when the required travel time has been completed.
14-3.10.2
Delays in Arriving at the First Stop.
Delay less than 1 minute
. Delays in arrival at the first stop of less than 1
minute may be ignored.
Delay in excess of 1 minute
. For delays in excess of 1 minute:
1.
Add the total delay to the bottom time.
CHAPTER 14 — Surface-Supplied Mixed-Gas Diving Procedures 14-15
2.
Recalculate the required decompression.
If no change in schedule is required, continue on the planned de-
compression.
If a change in schedule is required and the new schedule calls for
a decompression stop or stops deeper than the divers current
depth, perform any missed deeper stops at the divers current
depth. Do not go deeper.
Example.
If the delay time to arrival at the first stop is 3 minutes and 25 seconds,
round up to the next whole minute and add 4 minutes to the bottom time. Recheck
the decompression table to see if the decompression stop depths or times have
changed.
14-3.10.3
Delays in Leaving a Stop.
Ascent time between stops is not critical as it is in-
cluded in the time of the next stop.
Delay less than 1 minute
. When the delay is less than 1 minute, disregard the
delay.
Delay greater than 1 minute leaving a stop deeper than 50 fsw
. Add the delay
to the bottom time and recalculate the required decompression. If a new
schedule is required, pick up the new schedule at the present stop. Ignore any
missed stops or time deeper than the present stop.
Delays up to 5 minutes in leaving the 50-fsw and 40-fsw oxygen stops
.
Ignore the delay. Longer delays may be associated with an increased risk of
oxygen toxicity and should be avoided.
14-3.10.4
Delays in Travel from 40 fsw to the Surface.
Disregard any delays in travel from
40 fsw to the surface during surface decompression unless the diver exceeds the 5-
minute interval. When the diver exceeds the 5-minute interval, the diver shall be
treated for omitted decompression (see paragraph 14-4.10).
14-3.11
Special Procedures for Diving with an Oxygen Partial Pressure Greater Than 1.3
ata.
Limited gas supplies or system constraints may force some surface-supplied
helium-oxygen dives to be performed at oxygen partial pressures greater than 1.3
ata. Such dives place the diver at increased risk for CNS oxygen toxicity on the
bottom and require NAVSEA concurrence and CNO approval. Bottom times shall
be limited to those shown in Table 14-4.
14-3.11.1
Calculating Oxygen Partial Pressure.
The formula for calculating oxygen partial
pressure is:
ppO
2
%O
2
100
------------
D33+
33
----------------
×
=
14-16 U.S. Navy Diving Manual—Volume 3
Where:
ppO
2
= Oxygen partial pressure in ata
% O
2
= Oxygen percentage in the mixture
D = Divers depth in fsw
Example.
A diver is at 250 fsw breathing a 17.0 percent oxygen mixture. The
oxygen partial pressure is:
To dive in accordance with this section:
1.
Determine the bottom time that will be required to complete the task.
2.
From Table 14-4, select the oxygen partial pressure that corresponds to this
bottom time. If the bottom time is not exactly equal to the times listed in the
table, round to the next longer bottom time.
3.
Determine the deepest depth that will be attained by the diver during the dive.
4.
Calculate the maximum oxygen percentage that can be used by rearranging the
oxygen partial pressure equation to solve for the maximum oxygen percentage
that can be used:
Sample Problem.
A dive to a maximum depth of 270 fsw will require 35 minutes
of bottom time. Determine the maximum oxygen percentage that can be used for
this dive.
Table 14-4. Oxygen Partial Pressure Exposure Limits for Surface-Supplied HeO
2
Diving.
Oxygen Partial Pressure (ata) Maximum Bottom Time (min)
1.80 15
1.70 20
1.60 30
1.50 40
1.40 50
1.30 Unlimited
ppO
2
17
100
---------
250 33+
33
---------------------
×
=
1.46 ata=
%O
2
ppO
2
33
×
D33+
-------------------------
100
×
=
CHAPTER 14 — Surface-Supplied Mixed-Gas Diving Procedures 14-17
1.
Round the 35-minute bottom time to 40 minutes, the next longer bottom time
given in Table 14-7.
2.
The maximum allowable oxygen partial pressure for this bottom time is 1.50
ata.
3.
Calculate the maximum oxygen percentage:
14-3.11.2
Gas Mixtures.
Any gas mixture between the calculated maximum and minimum
values shown in the decompression table may be used to make the dive under the
provisions of this section.
14-3.11.3
Charting Surface-Supplied Helium-Oxygen Dives.
Figure 14-7 provides the
proper format for charting surface-supplied helium-oxygen dives.
14-4
SURFACE-SUPPLIED HELIUM-OXYGEN EMERGENCY PROCEDURES
In surface-supplied mixed-gas diving, specific procedures are used in emergency
situations. The following paragraphs detail these procedures. Other medical/phys-
iological factors that surface-supplied mixed-gas divers need to consider are
covered in detail in Volume 5. The U.S. Navy Treatment Tables are also presented
in Volume 5.
14-4.1
Bottom Time in Excess of the Table.
In the rare instance of diver entrapment or
umbilical fouling, bottom times may exceed 120 minutes, the longest value shown
in the table. When it is foreseen that bottom time will exceed 120 minutes, imme-
diately contact the Navy Experimental Diving Unit for advice on which
decompression procedure to follow. If advice cannot be obtained in time:
1.
Decompress the diver using the 120-minute schedule for the deepest depth
attained.
2.
Surface the diver after completing 30 minutes on oxygen at 40 fsw.
3.
Quickly recompress the diver to 60 fsw in the chamber.
4.
Treat the diver on Treatment Table 6 (Figure 21-8).
14-4.2
Loss of Helium-Oxygen Supply on the Bottom.
Follow this procedure if the
umbilical helium-oxygen supply is lost on the bottom:
1.
Shift the diver to the emergency gas system (EGS).
2.
Unless the loss is momentary, abort the dive.
%O
2
1.50 33
×
270 33+
----------------------
100
×
=
16.34=
14-18 U.S. Navy Diving Manual—Volume 3
Figure 14-7.
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Diving Chart.
CHAPTER 14 — Surface-Supplied Mixed-Gas Diving Procedures 14-19
3.
Remain on the EGS until arrival at the first water stop.
If the first water stop is an oxygen stop, shift to oxygen and complete
the decompression.
If the first stop is a helium-oxygen stop shallower than 160 fsw, shift to
air at the first stop and continue on the original decompression schedule
to 50 fsw.
If 60 percent helium/40 percent oxygen is available, upon reaching
100-fsw shift the divers to this mixture and continue on the original
decompression schedule to 50 fsw. Shift to oxygen at 50 fsw and com-
plete the decompression.
If the first stop is 160 fsw or deeper, delay the air shift to 150 fsw.
4.
If the EGS becomes exhausted before the first stop can be reached, shift the
diver to air, ascend to the first stop and continue as outlined above.
14-4.3
Inability to Shift to 40 Percent Oxygen at 100 fsw During Decompression.
If the
diver cannot be shifted to 60 percent helium/40 percent oxygen at 100 fsw during
decompression:
1.
Shift the diver to air.
2.
Follow the stops of the original decompression schedule to 50 fsw.
3.
Shift to oxygen at 50 fsw and complete the decompression as originally
planned.
14-4.4
Loss of Oxygen Supply at 50 fsw.
In the event that the diver cannot be shifted to
oxygen at 50 fsw or the oxygen supply is lost during the 50-fsw stop, take the
following action. If 60 percent helium/40 percent oxygen is available on the
console, shift the diver to that mixture. If 60 percent helium/40 percent oxygen is
not available, shift the diver to air. If the problem can be remedied quickly, reven-
tilate the diver with oxygen and resume the schedule at the point of interruption.
Consider any time on air or helium-oxygen as dead time. If the problem cannot be
remedied, keep the diver on air or helium-oxygen and use the Emergency Proce-
dures Decompression Table (Table 14-1) to complete the decompression. Any
time spent on oxygen at 50 fsw counts as decompression time on the Emergency
Procedures Decompression Table.
14-4.4.1
Unable to Shift to 60/40.
If it is not possible to shift the diver back to 60 percent
helium/40 percent oxygen, or if the 60 percent helium/40 percent oxygen supply is
also lost during the subsequent decompression, shift the diver to air and complete
the dive using the Emergency Procedures Decompression Table. Any time spent
on oxygen or 60 percent helium/40 percent oxygen counts toward decompression
time on the Emergency Procedures Decompression Table.
14-20 U.S. Navy Diving Manual—Volume 3
14-4.4.2
Surface Decompression from the Emegency Procedures Decompression
Table.
The diver can be surface decompressed from the Emergency Procedures
Decompression Table when the 30-fsw in-water stop is completed. Surface the
diver at 30 fsw/minute and recompress in the chamber to 40 fsw. The time from
leaving 30 fsw in the water to arriving at 40 fsw in the chamber cannot exceed 5
minutes. The number of oxygen breathing periods in the chamber is determined
with the same method as for normal surface decompression on the original
schedule.
14-4.5
Loss of Oxygen Supply at the 40-fsw Stop.
If the diver cannot be shifted to
oxygen at 40 fsw or the oxygen supply is lost during the 40-fsw stop, follow one
of the following procedures.
14-4.5.1
Oxygen Lost before Diver is within Emergency SUR D Limits.
If the loss occurs
before the diver is within emergency surface decompression limits, proceed as
follows:
1.
If 60 percent helium/40 percent oxygen is available on the console, shift the
diver to that mixture.
2.
If 60 percent helium/40 percent oxygen is not available, shift the diver to air.
3.
If the loss of oxygen can be remedied quickly, reventilate the divers with oxy-
gen and resume the schedule at the point of interruption. Consider any time on
air or helium-oxygen as dead time.
4.
If the loss of oxygen is permanent, have the divers remain on air or helium-
oxygen and use the Emergency Procedures Decompression Table to complete
the decompression. Time spent on oxygen at 40 fsw counts toward decompres-
sion on the Emergency Procedures Decompression Table. Surface
decompression can be used after completing the 30-fsw stop.
14-4.5.2
Diver is within Emergency SUR D Limits.
If the diver is within Emergency SUR
D limits when the oxygen supply is lost, shift the diver to air, surface the diver,
and complete decompression in accordance with Emergency SUR D procedures.
14-4.5.3
Diver is within Normal SUR D Limits.
If the diver is within Normal SUR D limits
when the oxygen supply is lost, shift the diver to air, surface the diver, and
complete decompression in accordance with Normal SUR D procedures.
14-4.5.4
Diver is in the Chamber.
If the loss occurs in the chamber, have the diver breathe
chamber air.
Temporary Loss
. Return the diver to oxygen breathing. Consider any air time
as dead time.
Permanent Loss
. Follow the Emergency Procedures Decompression Table to
the surface. Any time already spent on oxygen or air at 40 fsw counts toward
decompression time on the Emergency Procedures Decompression Table.
CHAPTER 14 — Surface-Supplied Mixed-Gas Diving Procedures 14-21
14-4.6
Oxygen Supply Contaminated with Helium-Oxygen.
If the oxygen supply be-
comes contaminated with helium-oxygen:
1.
Shift the divers to helium-oxygen or air, whichever has the highest percentage
of oxygen.
2.
Find the contamination source and correct the problem. Probable sources of
contamination include:
Accidental opening of the emergency gas supply (EGS) valve on the
MK 21 MOD 1
An improper valve line-up on the console.
3.
When the problem is corrected:
Shift the divers back to oxygen.
Ventilate each diver and verify voice change.
Ventilate each diver and listen for the gas-flow change over the
communications.
Once a gas-flow change is heard, continue to vent for an addi-
tional 10 seconds. If a gas flow change cannot be heard, ventilate
for a minimum of 20 seconds.
Restart the stop time. Disregard all previous time spent at the stop, i.e.,
treat as dead time.
14-4.7
Central Nervous System (CNS) Oxygen Toxicity Symptoms (Nonconvulsive) at
the 50-fsw Stop.
Follow this procedure if a diver exhibits CNS oxygen toxicity
symptoms at the 50-fsw stop:
1.
Bring the divers up 10 feet and shift to air to reduce the partial pressure of oxy-
gen. Shift the console as the divers are traveling.
2.
Upon reaching the 40-fsw stop, maintain communications as the buddy or
standby diver monitors the stricken diver.
3.
Ventilate both divers (the stricken diver first).
4.
SUR D after completing the 30-fsw stop on the Emergency Procedures
Decompression Table.
5.
Disregard the missed time at 50 fsw.
6.
If the diver convulses at 40 fsw in spite of these measures, follow the proce-
dures outlined in paragraph 14-4.9.
14-22 U.S. Navy Diving Manual—Volume 3
14-4.8
CNS Oxygen Toxicity Symptoms (Nonconvulsive) at the 40-fsw Stop.
14-4.8.1
Diver is not within Emergency Surface Decompression Limits.
If symptoms ap-
pear before the diver is within emergency surface decompression limits:
1.
Ascend to the 30-fsw stop and shift to air.
2.
Surface decompress after completing the 30-fsw stop on the Emergency Pro-
cedures Decompression Table.
3.
Disregard missed time at 40 fsw.
4.
If the diver convulses at 30 fsw in spite of these measures, follow the proce-
dures outlined in paragraph 14-4.9.
14-4.8.2
Diver is within Emergency Surface Decompression Limits.
If symptoms occur
after the diver is within emergency surface decompression limits, surface decom-
press the diver using emergency SUR D procedures.
14-4.8.3
Diver is within Normal Surface Decompression Limits.
If symptoms occur after
the diver is within normal surface decompression limits, surface decompress the
diver using normal SUR D procedures.
14-4.8.4
Diver is at a Chamber Stop.
If symptoms occur during the chamber stop:
1.
Remove the mask.
2.
Fifteen minutes after all symptoms have completely subsided, resume oxygen
breathing at the point of interruption.
3.
Complete all required oxygen breathing time. If the diver cannot tolerate oxy-
gen at all, complete decompression on chamber air using the stops of the
Emergency Procedures Decompression Table. All previous time on oxygen
and air at 40 fsw in the chamber counts toward decompression when a shift to
this table is made.
14-4.9
CNS Oxygen Convulsion at the 50-fsw Stop or 40-fsw Stop.
If oxygen symp-
toms advance to convulsions, or if the diver is presumed to be convulsing at the
50-fsw stop or 40-fsw stop, a serious emergency has developed. Only general
management guidelines can be presented here. Topside supervisory personnel
must take whatever action they deem necessary to bring the casualty under
control.
Follow these procedures when a diver is convulsing at the 50-fsw stop or the 40-
fsw stop:
1.
Shift the divers to air.
2.
Have the unaffected diver ventilate himself and then ventilate the stricken
diver.
CHAPTER 14 — Surface-Supplied Mixed-Gas Diving Procedures 14-23
3.
Hold the divers at depth until the tonic-clonic phase of the sequence has sub-
sided. The tonic-clonic phase of a convulsion generally lasts 1 to 2 minutes.
4.
If only one diver is in the water, launch the standby diver immediately and
have him ventilate the stricken diver.
5.
If consciousness is quickly regained and voice communication reestablished,
the stricken diver may be tended by the standby diver or the buddy diver and
decompressed according to one of two options:
If the diver was eligible for emergency or normal surface decompres-
sion prior to the seizure, allow a short period for stabilization and then
decompress using emergency or normal surface decompression
procedures.
If the diver was not eligible for emergency or normal surface decom-
pression, conduct decompression on the Emergency Procedures
Decompression Table. Surface decompress upon completing the 30 fsw
water stop.
6.
If communication is not reestablished when the tonic-clonic phase is presumed
past, but conditions are such that the standby diver or the buddy diver can ver-
ify that the affected diver is breathing and stable, conduct decompression on
the Emergency Procedures Decompression Table using surface decompres-
sion upon completion of the 30 fsw water stop.
7.
If it is not possible to verify that the affected diver is breathing because he can-
not be reached quickly enough or visibility will not permit an assessment, the
diver shall be surfaced at 40 fsw/min. In this situation, airway obstruction can-
not be ruled out and to remain at depth may be fatal. As the diver has 100
percent oxygen in his lungs prior to the seizure, approximately 2 minutes may
be allowed to lapse after the tonic-clonic phase ends before surfacing is initi-
ated. Although blood carbon dioxide will be high, oxygenation should be
adequate. The diver will almost certainly be unconscious and arterial gas
embolism cannot be ruled out. Such a diver should receive any necessary air-
way support, be recompressed to 60 fsw immediately and be treated for
arterial gas embolism in accordance with Figure 21-5.
14-4.10
Omitted Decompression.
Certain emergencies may interrupt or prevent required
decompression. Unexpected surfacing, exhausted gas supply and bodily injury are
examples of such emergencies. Table 14-5 shows the initial management steps to
be taken when the diver has uncontrolled ascent.
14-4.10.1
Blowup from a Depth Greater Than 50 fsw.
Blowup from a depth greater than 50
fsw when more than 60 minutes of decompression is missed is an extreme emer-
gency. The diver shall be returned as rapidly as possible to the full depth of the
dive or the deepest depth of which the chamber is capable, whichever is shallower.
14-24 U.S. Navy Diving Manual—Volume 3
14-4.10.2
For Saturation Systems.
For saturation systems, initial rapid compression on air
to 60 fsw, followed by compression on pure helium to the full depth of the dive (or
deeper if symptom onset warrants) is indicated. The diver shall breathe 84-percent
helium/16-percent oxygen by mask during the compression (if possible) to avoid
the possibility of hypoxia as a result of gas pocketing in the chamber. Once at the
saturation depth, the length of time spent can be dictated by the circumstances of
the diver, but should not be less than 2 hours. During this 2 hours, treatment gas
should be administered to the diver as outlined in Chapter 15, Chapter 15-23.8.2.
The chamber oxygen partial pressure should be allowed to fall passively to 0.44-
0.48 ata. Saturation decompression is begun without an upward excursion.
14-4.10.3
For Nonsaturation Systems.
For nonsaturation systems, the diver shall be
rapidly compressed on air to the depth of the dive or to 225 feet, whichever is shal-
lower. For compressions deeper than 165 feet, remain at depth for 30 minutes. For
compressions to 165 feet and shallower, remain at depth for a minimum of two
hours. Decompress on USN Treatment Table 8 for Deep Blowup (Table 14-6).
While deeper than 165 feet, a helium-oxygen mixture with 16-percent oxygen to
21-percent oxygen, if available, may be breathed by mask to reduce narcosis.
If the diver develops symptoms of decompression sickness or gas embolism
before recompression for omitted decompression can be accomplished, immediate
treatment using the appropriate oxygen or air recompression table is essential.
Guidance for table selection and use is given in Chapter 21. If the depth of the
Table 14-5. Management of Asymptomatic Omitted Decompression.
Deepest
Decompression
Stop Omitted
Decompression
Status
Surface
Interval
(Note 1)
Action
Nonsaturation System Saturation System
None No decompression stops
required
N/A Observe on surface for one
hour
Observe on surface for one
hour
50 fsw or shallow
Stops required. Within
normal or emergency SUR
D limits.
5
minutes
Follow normal or emergency
SUR D procedure
Follow normal or emergency
SUR D procedure
>
5 minutes
Treatment Table 5 Treatment Table 5
Stops required. Not within
emergency SUR D limits.
≤ 5
minutes
Treatment Table 5 Treatment Table 5
>
5 minutes
Treatment Table 6 Treatment Table 6
Deeper than 50
fsw
Stops required. Less than
60 minutes missed.
Any Treatment Table 6 Treatment Table 6
Stops required. Greater
than 60 minutes missed.
Any Compress to depth of dive
NTE 225 fsw. Use Treatment
Table 8.
Compress to depth of dive.
Saturate two hours. Use
saturation decompression
without an initial upward
excursion.
Note 1:
From stop to stop.
CHAPTER 14 — Surface-Supplied Mixed-Gas Diving Procedures 14-25
deepest stop omitted was greater than 50 fsw and more than 60 minutes of decom-
pression have been missed, use of Treatment Table 8 for Deep Blowup or
saturation treatment is indicated. On Treatment Tables 4 and 8, a 60-percent
helium/40-percent oxygen or 60-percent nitrogen/40-percent oxygen mixture may
be breathed as treatment gas at 165 fsw and shallower. At 60 fsw and shallower,
pure oxygen may be given to the diver as treatment gas. For all treatment gases
(HeO
2
, N
2
O
2
, and O
2
) a schedule of 25 minutes on gas and 5 minutes on chamber
Table 14-6. U.S. Navy Treatment Table 8 for Deep Blowup.
Depth (fsw)
Max Time at Initial Treatment Depth
(hours)
2-fsw Stop Times
(minutes)
225 0.5 5
165 3 12
140 5 15
120 8 20
100 11 25
80 15 30
60 Unlimited 40
40 Unlimited 60
20 Unlimited 120
1. Enter the table at the depth which is exactly equal to or next
g
reater than the deepest depth attained in the recompression.
The descent rate is as fast as tolerable.
2. The maximum time that can be spent at the deepest depth is shown in the second column. The maximum time for 225 fsw
is 30 minutes; for 165 fsw, three hours. For an asymptomatic diver, the minimum time at depth is 30 minutes for depths ex-
ceedin
g
165 fsw and two hours for depths equal to or shallower than 165 fsw.
3. Decompression is be
g
un with a 2-fsw reduction in pressure if the depth is an even number. Decompression is be
g
un with
a 3-fsw reduction in pressure if the depth is an odd number. Subsequent stops are carried out every 2 fsw. Stop times are
g
iven in column three. The stop time be
g
ins when leavin
g
the previous depth. Ascend to the next stop in approximately 30
seconds.
4. Stop times apply to all stops within the band up to the next quoted depth. For example, for ascent from 165 fsw, stops of 12
minutes are made at 162 fsw, and at every two-foot interval to 140 fsw. At 140 fsw, the stop time becomes 15 minutes.
When travelin
g
from 225 fsw, the 166-fsw stop is five minutes; the 164-fsw stop is 12 minutes. Once be
g
un, decompres-
sion is continuous. For example, when decompressin
g
from 225 feet, ascent is not halted at 165 fsw for three hours. How-
ever, ascent may be halted at 60 fsw and shallower for any desired period of time.
5. While deeper than 165 fsw, a helium-oxy
g
en mixture with 16-21 percent oxy
g
en may be breathed by mask to reduce nar-
cosis. At 165 fsw and shallower, a 60-percent helium/40-percent oxy
g
en mixture or a 60-percent nitro
g
en/40-percent oxy-
g
en mixture may be
g
iven to the diver as treatment
g
as. At 60 fsw and shallower, pure oxy
g
en may be
g
iven to the diver as
treatment
g
as. For all treatment
g
ases (HeO
2
, N
2
O
2
, and O
2
), a schedule of 25 minutes on
g
as and five minutes on cham-
ber air should be followed for a total of four cycles. Additional oxy
g
en may be
g
iven at 60 fsw after a two-hour interval of
chamber air. See USN Treatment Table 7 (Volume 5, Chapter 21) for
g
uidance.
6. To avoid loss of the chamber seal, ascent may be halted at four fsw and the total remainin
g
stop time of 240 minutes taken
at this depth. Ascend directly to the surface upon completion of the required time.
7. Total ascent time from 225 fsw is 56 hours, 29 minutes. For a 165-fsw recompression, total ascent time is 53 hours 52 min-
utes, and for a 60-fsw recompression, 36 hours, 0 minutes.
14-26 U.S. Navy Diving Manual—Volume 3
air should be followed for four cycles. Additional oxygen may be given at 60 fsw
and shallower after a 2-hour interval of chamber air. See USN Treatment Tables 4
and 7 (Chapter 21) for guidance on additional oxygen breathing.
In all cases of deep blowup, the services of a Diving Medical Officer shall be
sought at the earliest possible moment.
14-4.11
Light-Headed or Dizzy Diver on the Bottom.
Dizziness is a common term used to
describe a number of feelings, including light-headedness, unsteadiness, vertigo (a
sense of spinning), or the feeling that one might pass out. There are a number of
potential causes of dizziness in surface-supplied diving, including hypoxia, a gas
supply contaminated with toxic gases such as methylchloroform, and trauma to the
inner ear caused by difficult clearing of the ear. At the low levels of oxygen
percentage specified for surface-supplied diving, oxygen toxicity is an unlikely
cause unless the wrong gas has been supplied to the diver.
14-4.11.1
Initial Treatment.
The first step to take is to have the diver stop work and ventilate
the rig while topside checks the oxygen content of the supply gas. These actions
should eliminate hypoxia as a cause. If ventilation does not improve symptoms,
the cause may be a contaminated gas supply. Shift banks to the standby helium-
oxygen supply and continue ventilation. If the condition clears, isolate the contam-
inated bank for future analysis and abort the dive on the standby gas supply. If the
entire gas supply is suspect, place the diver on the EGS and abort the dive. Follow
the guidance of paragraph 14-4.2 for ascents.
14-4.11.2
Vertigo.
Vertigo due to inner ear problems will not respond to ventilation and in
fact may worsen. One form of vertigo, however, alternobaric vertigo, may be so
short-lived that it will disappear during ventilation. Alternobaric vertigo will
usually occur just as the diver arrives on the bottom and often can be related to a
difficult clearing of the ear. It would be unusual for alternobaric vertigo to occur
after the diver has been on the bottom for more than a few minutes. Longer lasting
vertigo due to inner ear barotrauma will not respond to ventilation and will be
accompanied by an intense sensation of spinning and marked nausea. Also, it is
usually accompanied by a history of difficult clearing during the descent. These
characteristic symptoms may allow the diagnosis to be made. A wide variety of
ordinary medical conditions may also lead to dizziness. These conditions may
occur while the diver is on the bottom. If symptoms of dizziness are not cleared by
ventilation and/or shifting to alternate gas supplies, have the dive partner or
standby diver assist the diver(s) and abort the dive.
14-4.12
Unconscious Diver on the Bottom.
An unconscious diver on the bottom consti-
tutes a serious emergency. Only general guidance can be given here. Management
decisions must be made on site, taking into account all known factors. The advice
of a Diving Medical Officer shall be obtained at the earliest possible moment.
If the diver becomes unconscious on the bottom:
1.
Make sure that the breathing medium is adequate and that the diver is breath-
ing.
CHAPTER 14 — Surface-Supplied Mixed-Gas Diving Procedures 14-27
2.
Check the status of any other divers.
3.
If there is any reason to suspect gas contamination, shift to the standby
helium-oxygen supply.
4.
Have the dive partner or standby diver ventilate the afflicted diver to remove
accumulated carbon dioxide in the helmet and ensure the correct oxygen
concentration.
5.
When ventilation is complete, have the dive partner or standby diver ascertain
whether the diver is breathing. In the MK 21, the presence or absence of breath
sounds will be audible over the intercom.
6.
If the diver appears not to be breathing, the dive partner/standby diver should
attempt to reposition the divers head to open the airway. Airway obstruction
will be the most common reason why an unconscious diver fails to breathe.
7.
Check afflicted diver for signs of consciousness:
If the diver has regained consciousness, allow a short period for stabili-
zation and then abort the dive.
If the diver remains unresponsive but is breathing, have the dive partner
or standby diver move the afflicted diver to the stage. This action need
not be rushed.
If the diver appears not to be breathing, make further attempts to open
the airway while moving the diver rapidly to the stage.
8.
Once the diver is on the stage, observe again briefly for the return of
consciousness.
If consciousness returns, allow a period for stabilization, then begin
decompression.
If consciousness does not return, bring the diver to the first decompres-
sion stop at a rate of 30 fsw/min (or to the surface if the diver is in a no-
decompression status).
9.
At the first decompression stop:
If consciousness returns, decompress the diver on the standard decom-
pression schedule using normal surface decompression.
If the diver remains unconscious but is breathing, decompress on the
standard decompression schedule and plan on emergency surface
decompression from 40 fsw. If consciousness returns during ascent, use
normal surface decompression.
If the diver remains unconscious and breathing cannot be detected in
spite of repeated attempts to position the head and open the airway, an
14-28 U.S. Navy Diving Manual—Volume 3
extreme emergency exists. One must weigh the risk of catastrophic,
even fatal, decompression sickness if the diver is brought to the sur-
face, versus the risk of asphyxiation if the diver remains in the water.
As a general rule, if there is any doubt about the divers breathing
status, assume he is breathing and continue normal decompression in
the water. If it is absolutely certain that the diver is not breathing, leave
the unaffected diver at his first decompression stop to complete decom-
pression and surface the affected diver at 30 fsw/minute, deploying the
standby diver as required. Recompress immediately and treat for
omitted decompression according to Table 14-5.
14-4.13
Decompression Sickness in the Water.
Decompression sickness may develop in
the water during surface-supplied diving. This possibility is one of the prime
reasons for limiting dives to 300 fsw and allowing exceptional exposures only
under emergency circumstances. The symptoms of decompression sickness may
be joint pain or more serious manifestations such as numbness, loss of muscular
function, or vertigo.
14-4.13.1
Management.
Management of decompression sickness in the water will be diffi-
cult under the best of circumstances. Only general guidance can be presented here.
Management decisions must be made on site taking into account all known
factors. The advice of a Diving Medical Officer shall be obtained at the earliest
possible moment.
14-4.13.2
Deeper than 50 fsw.
If symptoms of decompression sickness occur deeper than
50 fsw, recompress the diver 10 fsw. Shift to a 60 percent helium/40 percent
oxygen mixture if the diver is not already on that mixture. Remain at the deeper
stop for 1.5 times the stop time called for in the decompression table. If no stop
time is indicated in the table, use the next shallower stop time to make the calcula-
tion. If symptoms resolve or stabilize at an acceptable level, decompress the diver
to the 50 fsw water stop by multiplying each intervening stop time by 1.5 or more
as needed to control the symptoms. Shift to 100 percent oxygen at 50 fsw and take
the standard 50-fsw stop. Ascend to 40 fsw and take a 30-minute stop on oxygen,
then surface decompress and treat on Treatment Table 6. If during this scenario,
symptoms worsen to the point that it is no longer practical for the diver to remain
in the water, surface the diver and follow the guidelines for symptomatic omitted
decompression outlined in Chapter 21 of Volume 5.
14-4.13.3
At 50 fsw and Shallower.
Symptoms developing at the 50-fsw and 40-fsw oxygen
breathing stops can represent either decompression sickness or oxygen toxicity.
Oxygen toxicity will be a much more common occurrence. To avoid potential
error in diagnosis, all symptoms with the exception of joint pain shall initially be
considered oxygen toxicity and be treated accordingly. If the case is clearly
decompression sickness, remain at the stop. Resolution of symptoms may occur as
oxygen breathing continues.
14-4.13.4
Resolution/Nonresolution.
If resolution occurs, resume the decompression, use
normal surface decompression and treat on Treatment Table 6. If symptoms are
CHAPTER 14 — Surface-Supplied Mixed-Gas Diving Procedures 14-29
not resolved within 20 minutes at 50 fsw or within 30 minutes at 40 fsw, or have
worsened to the point it is no longer practical for the diver to remain in the water,
surface the diver and treat on Treatment Table 6. If symptoms originally thought
to be oxygen toxicity persist or worsen following an “up ten and shift” procedure
and are now felt to be decompression sickness, shift the diver to 100 percent
oxygen, recompress 10 fsw and repeat the missed stop. Follow the guidance for
resolution/nonresolution of symptoms as previously outlined.
14-30 U.S. Navy Diving Manual—Volume 3
Table 14-7.
Surface-Supplied Helium-Oxygen Decompression Table.
Depth
(fsw)
Bottom
Time
(min.)
Time to
(min:sec)
Decompression Stops (fsw)
Total
Ascent
Time*
(min:sec)
190
180
170
160
150
140
130
120
110
100
90
80
70
60
50
40
BOTTOM MIX
100% O
2
60
Max O
2
= 40.0%
Min O
2
= 16.0%
10
2:00
0
2:00
20
2:00
0
2:00
30
2:00
0
2:00
40
2:00
0
2:00
60
0:40
24
24:40
80
0:40
32
32:40
100
0:40
40
40:40
120
0:40
42
42:40
70
Max O
2
= 40.0%
Min O
2
= 16.0%
10
2:20
0
2:20
20
2:20
0
2:20
30
2:20
0
2:20
40
1:00
23
24:00
60
1:00
35
36:00
80
1:00
45
46:00
100
1:00
50
51:00
120
1:00
55
56:00
80
Max O
2
= 38.0%
Min O
2
= 16.0%
10
2:40
0
2:40
20
2:40
0
2:40
25
2:40
0
2:40
30
1:20
24
25:20
40
1:20
31
32:20
60
1:20
47
48:20
80
1:20
56
57:20
100
1:20
63
64:20
120
1:20
67
68:20
90
Max O
2
= 34.9%
Min O
2
= 16.0%
10
3:00
0
3:00
20
3:00
0
3:00
30
1:40
31
32:40
40
1:40
39
40:40
60
1:40
56
57:40
80
1:40
67
68:40
100
1:40
75
76:40
120
1:40
78
79:40
100
Max O
2
= 32.3%
Min O
2
= 16.0%
10
3:20
0
3:20
15
3:20
0
3:20
20
2:00
25
27:00
30
2:00
36
38:00
40
2:00
47
49:00
60
2:00
66
68:00
80
2:00
77
79:00
100
2:00
84
86:00
120
2:00
87
89:00
* Does not include oxygen shiftover time.
CHAPTER 14 — Surface-Supplied Mixed-Gas Diving Procedures 14-31
Table 14-7.
Surface-Supplied Helium-Oxygen Decompression Table (Continued).
Depth
(fsw)
Bottom
Time
(min.)
Time to
First Stop
(min:sec)
Decompression Stops (fsw)
Total
Ascent
Time*
(min:sec)
190
180
170
160
150
140
130
120
110
100
90
80
70
60
50
40
BOTTOM MIX
100% O
2
110
Max O
2
= 30.0%
Min O
2
= 16.0%
10
2:20
16
18:20
20
2:20
29
31:20
30
2:20
42
44:20
40
2:20
53
55:20
60
2:20
73
75:20
80
2:20
88
88:20
100
2:20
92
94:20
120
2:20
96
98:20
120
Max O
2
= 28.0%
Min O
2
= 16.0%
10
2:40
19
21:40
20
2:40
34
36:40
30
2:40
49
51:40
40
2:40
62
64:40
60
2:40
82
84:40
80
2:40
94
96:40
100
2:40
99
101:40
120
2:20
10
97
109:20
130
Max O
2
= 26.3%
Min O
2
= 16.0%
10
2:40
10
11
23:40
20
2:40
10
28
40:40
30
2:40
10
45
57:40
40
2:20
7
10
59
78:20
60
2:20
7
10
78
97:20
80
2:20
7
10
90
102:20
100
2:20
7
10
96
115:20
120
2:20
7
11
98
118:20
140
Max O
2
= 24.8%
Min O
2
= 16.0%
10
3:00
10
11
24:00
20
10
28
41:00
30
3:00
10
45
58:00
40
7
10
59
78:40
60
2:40
7
10
78
97:40
80
7
10
90
109:40
100
2:40
7
10
96
115:40
120
7
11
98
118:40
150
Max O
2
= 23.4%
Min O
2
= 16.0%
10
3:20
10
12
25:20
20
7
10
33
53:00
30
3:00
7
10
50
70:00
40
7
10
65
85:00
60
3:00
7
10
84
104:00
80
7
10
96
116:00
100
3:00
7
13
99
122:00
120
9
16
99
127:00
* Does not include oxygen shiftover time.
Exceptional Exposure times are surrouned by the black box.
14-32 U.S. Navy Diving Manual—Volume 3
Table 14-7.
Surface-Supplied Helium-Oxygen Decompression Table (Continued).
Depth
(fsw)
Bottom
Time
(min.)
Time to
First Stop
(min:sec)
Decompression Stops (fsw)
Total
Ascent
Time*
(min:sec)
190
180
170
160
150
140
130
120
110
100
90
80
70
60
50
40
BOTTOM MIX
100% O
2
160
Max O
2
= 22.2%
Min O
2
= 16.0%
10
3:20
7
10
15
35:20
20
3:20
7
10
36
56:20
30
3:20
7
10
55
75:20
40
3:20
7
10
70
90:20
60
3:00
7
6
10
83
109:00
80
3:00
7
9
10
98
127:00
100
3:00
7
13
14
98
135:00
120
3:00
7
17
16
98
142:00
170
Max O
2
= 21.1%
Min O
2
= 16.0%
10
3:20
7
0
10
17
37:20
20
3:20
7
0
10
41
61:20
30
3:20
7
1
10
62
83:20
40
3:20
7
4
10
77
101:20
60
3:20
7
10
10
92
122:20
80
3:20
9
14
13
96
137:20
100
3:00
7
5
18
15
99
147:20
120
3:00
7
9
21
16
99
155:20
180
Max O
2
= 20.1%
Min O
2
= 16.0%
10
3:40
7
0
10
20
40:40
20
3:40
7
0
10
44
64:40
30
3:40
7
4
10
67
91:40
40
3:20
7
0
8
10
81
109:20
60
3:20
7
5
11
10
96
132:20
80
3:20
7
9
15
15
99
148:20
100
3:20
7
13
19
16
99
157;20
120
3:20
7
17
23
16
99
165:20
190
Max O
2
= 19.2%
Min O
2
= 16.0%
10
4:00
7
0
10
22
43:00
20
3:40
7
0
2
10
50
72:40
30
3:40
7
0
7
10
69
96:40
40
3:40
7
4
9
10
84
117:40
60
3:40
7
9
13
12
93
137:40
80
3:20
7
3
13
18
15
99
158:20
100
3:20
7
6
16
21
16
99
168:20
120
3:20
7
8
20
23
16
99
176:20
200
Max O
2
= 18.4%
Min O
2
= 16.0%
10
4:00
7
0
1
10
25
46:00
20
4:00
7
0
4
10
53
78:00
30
3:40
7
0
3
7
10
74
104:40
40
3:40
7
0
7
10
10
86
123:40
60
3:40
7
4
10
14
13
98
149:40
80
3:40
7
8
14
18
16
99
165:40
100
3:40
7
12
17
23
16
99
177:40
120
3:40
8
15
21
23
18
99
185:40
* Does not include oxygen shiftover time.
Exceptional Exposure times are surrouned by the black box.
CHAPTER 14 — Surface-Supplied Mixed-Gas Diving Procedures 14-33
Table 14-7.
Surface-Supplied Helium-Oxygen Decompression Table (Continued).
Depth
(fsw)
Bottom
Time
(min.)
Time to
First Stop
(min:sec)
Decompression Stops (fsw)
Total
Ascent
Time*
(min:sec)
190
180
170
160
150
140
130
120
110
100
90
80
70
60
50
40
BOTTOM MIX
40% O
2
100% O
2
210
Max O
2
= 17.7%
Min O
2
= 12.0%
10
4:20
7
0
0
10
28
49:20
20
4:00
7
0
1
6
10
57
85:00
30
4:00
7
0
6
7
10
79
113:00
40
4:00
7
3
9
10
10
90
133:00
60
3:40
7
0
9
11
17
13
98
158:40
80
3:40
7
3
11
15
20
13
99
171:40
100
3:40
7
6
14
19
23
16
99
187:40
120
3:40
7
8
18
23
23
16
99
197:40
220
Max O
2
= 17.0%
Min O
2
= 12.0%
10
4:40
7
0
2
10
30
53:40
20
4:20
7
0
3
7
10
61
92:20
30
4:20
7
2
6
9
10
81
119:20
40
4:00
7
0
6
9
11
10
93
140:00
60
4:00
7
4
9
12
18
14
99
167:00
80
4:00
7
8
12
17
21
16
99
184:00
100
4:00
7
12
15
20
23
16
99
196:00
120
4:00
8
14
19
23
23
16
99
206:00
230
Max O
2
= 16.3%
Min O
2
= 12.0%
10
4:40
7
0
0
3
10
33
57:40
20
4:20
7
0
1
4
7
10
65
98:20
30
4:20
7
0
5
7
10
10
85
128:20
40
4:00
7
0
3
7
9
13
11
95
149:00
60
4:00
7
0
8
10
14
18
15
99
175:00
80
4:00
7
3
10
14
18
23
16
99
194:00
100
4:00
7
6
12
17
23
23
16
99
207:00
120
4:00
7
7
16
19
23
23
16
99
214:00
240
Max O
2
= 15.7%
Min O
2
= 12.0%
10
4:40
7
0
0
2
4
10
35
62:40
20
7
0
2
5
7
10
68
103:40
30
4:20
7
0
2
6
7
10
10
87
133:20
40
7
0
5
8
9
14
12
96
155:20
60
4:20
7
4
8
11
14
19
16
99
182:20
80
7
7
11
16
18
23
16
99
201:20
100
4:20
7
10
14
19
23
23
16
99
215:20
120
7
3
12
17
19
23
23
16
99
223:00
250
Max O
2
= 15.2%
Min O
2
= 12.0%
10
5:00
7
0
0
2
4
10
37
65:00
20
7
0
0
3
7
7
10
70
108:40
30
4:40
7
0
4
6
8
10
10
89
138:40
40
7
2
5
9
9
14
13
96
159:40
60
4:20
7
0
7
9
12
16
21
16
99
191:20
80
7
3
9
13
15
21
23
16
99
210:20
100
4:20
7
6
11
14
19
23
23
16
99
222:20
120
7
8
13
19
20
23
23
16
99
232:20
* Does not include oxygen shiftover time.
Exceptional Exposure times are surrouned by the black box.
14-34 U.S. Navy Diving Manual—Volume 3
Table 14-7.
Surface-Supplied Helium-Oxygen Decompression Table (Continued).
Depth
(fsw)
Bottom
Time
(min.)
Time to
First Stop
(min:sec)
Decompression Stops (fsw)
Total
Ascent
Time*
(min:sec)
190
180
170
160
150
140
130
120
110
100
90
80
70
60
50
40
BOTTOM MIX
40% O
2
100% O
2
260
Max O
2
= 14.6%
Min O
2
= 12.0%
10
5:00
7
0
0
0
4
4
10
40
70:00
20
5:00
7
0
2
4
6
7
10
74
115:00
30
4:40
7
0
2
5
6
9
10
10
92
145:40
40
4:40
7
0
3
8
9
10
15
14
96
166:40
60
4:40
7
3
7
10
14
16
21
16
99
197:40
80
4:40
7
6
10
13
17
23
23
16
99
218:40
100
4:20
7
2
9
13
16
20
23
23
16
99
232:20
120
4:20
7
4
11
14
19
20
23
23
16
99
240:20
270
Max O
2
= 14.2%
Min O
2
= 12.0%
10
5:20
7
0
0
2
3
4
10
42
73:20
20
5:00
7
0
0
2
6
6
8
10
78
122:00
30
5:00
7
0
3
6
6
9
13
10
93
152:00
40
4:40
7
0
2
5
8
8
12
16
13
98
173:40
60
4:40
7
0
6
8
10
14
19
23
16
99
206:40
80
4:40
7
3
8
11
14
17
23
23
16
99
225:40
100
4:40
7
5
11
13
16
20
23
23
16
99
237:40
120
4:40
7
8
12
16
19
20
23
23
18
99
247:40
280
Max O
2
= 13.7%
Min O
2
= 12.0%
10
5:40
7
0
0
3
3
4
10
46
78:40
20
5:20
7
0
0
4
6
7
7
10
81
127:20
30
5:00
7
0
1
5
5
9
9
12
10
96
159:00
40
5:00
7
0
4
6
8
9
12
17
15
98
181:00
60
5:00
7
4
6
8
12
15
18
23
16
99
213:00
80
4:40
7
0
7
9
11
15
17
23
23
16
99
231:40
100
4:40
7
2
9
11
15
17
20
23
23
16
99
246:40
120
4:40
7
4
11
13
16
19
20
23
23
16
99
255:40
290
Max O
2
= 13.3%
Min O
2
= 12.0%
10
5:40
7
0
0
0
4
3
4
10
49
82:40
20
7
0
0
2
6
6
6
9
10
83
134:20
30
5:20
7
0
2
5
5
9
9
14
12
94
162:20
40
7
0
5
7
8
11
13
17
15
98
186:20
60
5:00
7
0
6
7
9
12
15
20
23
16
99
219:00
80
7
2
8
10
12
16
19
23
23
16
99
240:00
100
5:00
7
5
10
12
15
19
20
23
23
16
99
254:00
120
7
8
11
16
17
19
20
23
23
16
99
264:00
300
Max O
2
= 12.9%
Min O
2
= 12.0%
10
6:00
7
0
0
0
4
3
4
10
49
83:00
20
7
0
0
2
6
6
6
9
10
83
134:40
30
5:40
7
0
2
5
5
9
9
14
12
94
162:40
40
7
0
5
7
8
11
13
17
15
98
186:40
60
5:20
7
0
6
7
9
12
15
20
23
16
99
219:20
80
7
2
8
10
12
16
19
23
23
16
99
240:20
100
5:20
7
5
10
12
15
19
20
23
23
16
99
254:20
120
7
8
11
16
17
19
20
23
23
16
99
264:20
* Does not include oxygen shiftover time.
Exceptional Exposure times are surrouned by the black box.
CHAPTER 14 — Surface-Supplied Mixed-Gas Diving Procedures 14-35
Table 14-7.
Surface-Supplied Helium-Oxygen Decompression Table (Continued).
Depth
(fsw)
Bottom
Time
(min.)
Time to
First Stop
(min:sec)
Decompression Stops (fsw)
Total
Ascent
Time*
(min:sec)
190
180
170
160
150
140
130
120
110
100
90
80
70
60
50
40
BOTTOM MIX
40% O
2
100% O
2
310
Max O
2
= 12.5%
Min O
2
= 10.0%
10
6:00
7
0
0
0
3
3
3
7
10
54
93:00
20
5:40
7
0
0
2
4
5
6
7
10
10
85
141:40
30
5:40
7
0
2
4
5
7
8
11
15
13
98
175:40
40
5:20
7
0
1
4
6
7
8
12
15
19
16
99
199:20
60
5:20
7
0
5
6
9
11
13
17
20
23
16
99
231:20
80
5:20
7
3
7
9
11
13
17
20
23
23
16
99
253:20
100
5:20
7
5
9
11
13
17
19
20
23
23
16
99
267:20
120
5:20
7
7
12
13
16
17
19
20
23
23
16
99
277:20
320
Max O
2
= 12.2%
Min O
2
= 10.0%
10
6:20
7
0
0
0
4
3
3
7
10
56
96:20
20
6:00
7
0
0
3
5
5
6
8
10
10
88
148:00
30
5:40
7
0
0
4
4
6
7
9
11
17
13
98
181:40
40
4:40
7
0
4
4
6
7
9
12
16
20
16
99
205:40
60
5:20
7
0
2
6
8
9
11
14
17
23
23
16
99
240:20
80
5:20
7
0
6
8
8
13
14
19
20
23
23
16
99
261:20
100
5:20
7
2
7
10
13
16
17
19
20
23
23
16
99
277:20
120
5:20
7
4
9
12
13
16
17
19
20
23
23
16
99
283:20
330
Max O
2
= 11.8%
Min O
2
= 10.0%
10
6:20
7
0
0
0
2
3
3
4
7
10
59
101:20
20
6:00
7
0
0
2
3
4
6
5
10
10
10
90
153:00
30
6:00
7
0
1
4
5
6
8
8
13
17
14
98
187:00
40
5:40
7
0
1
4
5
7
7
10
12
17
22
16
99
212:40
60
5:40
7
0
5
6
8
9
11
15
20
23
23
16
99
247:40
80
5:40
7
2
7
8
10
13
15
19
20
23
23
16
99
267:40
100
5:40
7
5
9
9
13
16
17
19
20
23
23
16
99
281:40
120
5:20
7
1
7
10
13
15
16
17
19
20
23
23
16
99
291:20
340
Max O
2
= 11.5%
Min O
2
= 10.0%
10
6:40
7
0
0
0
3
3
3
4
7
10
61
104:40
20
7
0
0
2
4
5
7
8
9
10
10
90
158:20
30
6:00
7
0
0
3
5
5
6
8
9
13
18
14
98
192:00
40
7
0
2
4
6
7
8
10
13
16
22
16
99
216:00
60
5:40
7
0
3
5
6
9
10
13
16
18
21
23
16
99
251:40
80
7
0
7
7
8
11
13
15
19
20
23
23
16
99
273:40
100
5:40
7
2
8
8
12
13
16
17
19
20
23
23
16
99
288:40
120
7
4
9
11
13
15
16
17
19
20
23
23
16
99
297:40
350
Max O
2
= 11.2%
Min O
2
= 10.0%
10
6:40
7
0
0
0
2
2
3
3
5
7
10
64
109:40
20
7
0
0
4
4
5
5
7
9
13
10
94
164:20
30
6:20
7
0
1
4
4
5
7
8
11
13
18
14
99
197:20
40
7
0
1
5
6
7
8
11
14
17
23
16
99
223:00
60
6:00
7
0
5
5
8
8
11
12
16
19
23
23
16
99
258:00
80
7
2
7
10
11
13
17
19
20
23
23
16
99
280:00
100
5:40
7
0
6
8
9
11
15
16
17
19
20
23
23
16
99
294:40
120
7
1
7
9
14
15
16
17
19
20
23
23
16
99
303:40
* Does not include oxygen shiftover time.
Exceptional Exposure times are surrouned by the black box.
14-36 U.S. Navy Diving Manual—Volume 3
Table 14-7. Surface-Supplied Helium-Oxygen Decompression Table (Continued).
Depth
(fsw)
Bottom
Time
(min.)
Time to
First Stop
(min:sec)
Decompression Stops (fsw)
Total
Ascent
Time*
(min:sec)
190
180
170
160
150
140
130
120
110
100
90
80
70
60
50
40
BOTTOM MIX
40% O
2
100% O
2
360
Max O
2
= 10.9%
Min O
2
= 10.0%
10
7:00
7
0
0
0
2
2
2
3
7
7
10
66
113:00
20
6:40
7
0
0
2
3
4
5
5
8
10
13
10
94
167:40
30
6:20
7
0
0
3
3
5
6
7
8
11
13
19
15
99
202:20
40
6:20
7
0
2
4
5
7
7
9
10
14
20
23
16
99
229:20
60
6:20
7
2
5
6
7
9
11
14
16
19
23
23
16
99
263:20
80
6:00
7
0
6
6
8
11
12
14
16
19
20
23
23
16
99
286:00
100
6:00
7
2
7
8
11
13
13
16
17
19
20
23
23
16
99
300:00
120
6:00
7
4
8
10
12
14
15
16
17
19
20
23
23
16
99
309:00
370
Max O
2
= 10.6%
Min O
2
= 10.0%
10
7:00
7
0
0
0
0
3
3
3
3
7
7
10
68
118:00
20
6:40
7
0
0
0
3
4
4
5
5
8
10
13
12
94
171:40
30
6:20
7
0
0
2
3
4
4
7
7
8
11
16
19
16
99
209:20
40
6:20
7
0
0
4
4
5
6
8
10
11
14
20
23
16
99
233:20
60
6:20
7
0
4
5
7
8
9
11
13
17
20
23
23
16
99
268:20
80
6:00
7
0
3
6
7
9
10
12
15
17
19
20
23
23
16
99
292:00
100
6:00
7
0
6
7
9
10
14
15
16
17
19
20
23
23
16
99
307:00
120
6:00
7
1
7
9
11
13
14
15
16
17
19
20
23
23
16
99
316:00
380
Max O
2
= 10.4%
Min O
2
= 10.0%
10
7:20
7
0
0
0
0
3
3
3
3
7
7
10
68
118:20
20
7:00
7
0
0
0
3
4
4
5
5
8
10
13
12
94
172:00
30
6:40
7
0
0
2
3
4
4
7
7
8
11
16
19
16
99
209:40
40
6:40
7
0
0
4
4
5
6
8
10
11
14
20
23
16
99
233:40
60
6:40
7
0
4
5
7
8
9
11
13
17
20
23
23
16
99
268:40
80
6:20
7
0
3
6
7
9
10
12
15
17
19
20
23
23
16
99
292:20
100
6:20
7
0
6
7
9
10
14
15
16
17
19
20
23
23
16
99
307:20
120
6:20
7
1
7
9
11
13
14
15
16
17
19
20
23
23
16
99
316:20
* Does not include oxygen shiftover time.
Exceptional Exposure times are surrouned by the black box.