CHAPTER 15 — Saturation Diving 15-1
The purpose of this chapter is to familiarize divers with U.S. Navy satu-
ration diving systems and deep diving equipment.
Saturation diving is used for deep salvage or recovery using U.S. Navy
deep diving systems or equipment. These systems and equipment are designed to
support personnel at depths to 1000 fsw for extended periods of time.
The Deep Diving System (DDS) is a versatile tool in diving and its application is
extensive. Most of today’s systems employ a multilock deck decompression
chamber (DDC) and a personnel transfer capsule (PTC).
Non-Saturation Diving
. Non-saturation diving can be accomplished with the
PTC pressurized to a planned depth. This mode of operation has limited real
time application and therefore is seldom used in the U.S. Navy.
Saturation Diving
. Underwater projects that demand extensive bottom time
(i.e., large construction projects, submarine rescue, and salvage) are best con-
ducted with a DDS in the saturation mode.
Conventional Diving Support
. The DDC portion of a saturation system can be
employed as a recompression chamber in support of conventional, surface-
supplied diving operations.
The configuration and the specific equipment composing a deep diving system
vary greatly based primarily on the type mission for which it is designed. Modern
systems however, have similar major components that perform the same functions
despite their actual complexity. Major components include a PTC, a PTC handling
system, and a DDC.
Personnel Transfer Capsule.
The PTC (Figure 15-1) is a spherical, submersible
pressure vessel that can transfer divers in full diving dress, along with work tools
and associated operating equipment, from the deck of the surface platform to their
designated working depth.
Gas Supplies.
During normal diving operations, the divers’ breathing and PTC
gas are supplied from the surface through a gas supply hose. In addition, all PTCs
15-2 U.S. Navy Diving Manual—Volume 3
carry emergency supplies of helium, helium-oxygen, and oxygen in externally
mounted flasks. Internal PTC pressure, gas supply pressures, and water depth are
continuously monitored from the PTC.
The typical helium system is designed to maintain PTC pressurization and purge
oxygen from all PTC electrical units to alleviate any fire hazard.
The helium-oxygen mixed-gas system consists of an internal built-in breathing
system (BIBS) with associated valves, piping, and fittings. The mixed-gas system
supplies emergency breathing gas to the diver umbilicals when the topside supply
is interrupted, and supplies the BIBS if the internal PTC atmosphere is
PTC Pressurization/Depressurization System.
The gas supply and exhaust
system control and regulate internal PTC pressure. Relief valves and manual vent
valves prevent overpressurization of the PTC in case a line rupture causes a full
flask to discharge into the PTC. Needle valves are employed to control depressur-
ization. Depth gauges, calibrated in feet of seawater, monitor internal and external
PTC depth. Equalization and vent valves are also provided for the access trunk.
Figure 15-1.
Typical Personnel Transfer Capsule Exterior.
CHAPTER 15 — Saturation Diving 15-3
PTC Life-Support System.
The life-support equipment for the PTC includes
carbon dioxide scrubbers, a gas supply to provide metabolic oxygen, oxygen, and
carbon dioxide analyzers.
Electrical System.
The electrical system uses a multiple voltage distribution
system that may be used for heating, internal and external lighting, instrumenta-
tion, and communications. Power for normal PTC operation is surface-supplied
and is transmitted through power and communications cables. A battery supplies
critical loads such as atmosphere monitoring, emergency CO
scrubber, and
communications if the surface-supplied power is interrupted.
Communications System.
A typical communications system is divided into four
individual systems to ensure efficient operation under a variety of conditions.
Hardwire Intercom System
. The intercom system is an amplified voice system
employing a helium speech unscrambler providing communications within the
PTC and between the Main Control Console (MCC), divers, deck winch oper-
ator, Deck Officer, and the DDCs.
Underwater Mobile Sound Communications Set (UQC)
. The UQC system is a
wireless emergency system providing voice communications between the PTC
and underwater telephone system of the attending ship. The UQC system is
used if the power and communications cables fail or are disconnected.
Closed-Circuit Television (CCTV)
. The CCTV consists of video channels from
the PTC to the MCC. Cameras are usually mounted outside the PTC.
Sound-Powered Phones
. The PTC is equipped with a sound-powered phone
system for communication with the MCC in case the normal system is lost.
Strength, Power, and Communications Cables (SPCCs).
The strength, power,
and communications cables typically provide electrical power, wired communica-
tions, instrumentation signals, a strength member, and coaxial transmission
(CCTV signals) between the MCC and the PTC.
PTC Main Umbilical.
The typical PTC main umbilical consists of a breathing-gas
supply hose, a hot water hose, a pneumofathometer, and a strength member.
Diver Hot Water System.
Hot water may be necessary when conducting satura-
tion dives. The surface ship supplies hot water via the PTC main umbilical to the
diver’s suit and breathing gas heater. The PTC operator monitors the water
temperature and ensures that the flow is adequate.
Deck Decompression Chamber (DDC).
The DDC furnishes a dry environment
for accomplishing decompression and, if necessary, recompression. The DDC is a
multi-compartment, horizontal pressure vessel mounted on the surface-support
platform. Each DDC is equipped with living, sanitary, and resting facilities for the
dive team. A service lock provides for the passage of food, medical supplies, and
15-4 U.S. Navy Diving Manual—Volume 3
other articles between the diving crew inside the chamber and topside support
DDC Life-Support System (LSS).
The DDC Life Support-System maintains the
chamber environment within acceptable limits for the comfort and safety of the
divers. The typical system consists of temperature and humidity control, carbon
dioxide removal, and equipment monitoring. Processing consists of filtering
particulate matter, removing carbon dioxide and gaseous odors, and controlling
heat and humidity.
Sanitary System.
The sanitary system consists of hot and cold water supplies for
operating the wash basin, shower, and head. Waste from the head discharges into a
separate holding tank for proper disposal through the support platform’s collec-
tion, holding, and transfer system.
Fire Suppression System.
All DDCs have fire-fighting provisions ranging from
portable fire extinguishers to installed, automatic systems. DDCs and recompres-
sion chambers have similar hyperbaric flammability hazards. Ignition sources and
combustion materials should be minimized during critical fire zone times. (At the
normal operating depth of PTCs, the oxygen concentration will not support
combustion, so they have no built-in fire-fighting equipment.)
Main Control Console (MCC).
The MCC is a central control and monitoring area.
The MCC houses the controls for the gas supply and atmosphere analysis for the
DDC, atmosphere monitoring for the PTC, pressure gauges for gas banks, clocks,
communications systems controls, recorders, power supplies, and CCTV monitors
and switches for the DDC and PTC.
Gas Supply Mixing and Storage.
The DDC gas system provides oxygen, helium-
oxygen mixtures, helium, and air for pressurization and diver life support. A BIBS
is installed in every lock for emergency breathing in contaminated atmospheres, as
well as for administering treatment gas during recompression treatment. Normal
pressurizing or depressurizing of the DDC is done from the MCC. A means of
sampling the internal atmosphere is provided for monitoring carbon dioxide and
oxygen partial pressure. An oxygen-addition system maintains oxygen partial
pressure at required levels. A pressure-relief system prevents overpressurization of
the chamber.
A DDS should be outfitted with gas-mixing equipment, commonly referred to as a
“Mixmaker,” which provides additional flexibility when conducting deep satura-
tion diving. The Mixmaker can provide mixed gas at precise percentages and
quantities needed for any given dive. If necessary, the gas coming from the
Mixmaker can be sent directly to the divers for consumption.
PTC Handling Systems.
Of all the elements of DDS, none are more varied than
PTC handling systems. Launch and retrieval of the PTC present significant
hazards to the divers during heavy weather and are major factors in configuring
and operating the handling system.
CHAPTER 15 — Saturation Diving 15-5
Handling System Characteristics.
All handling systems have certain common
characteristics. The system should:
Be adequately designed and maintained to withstand the elements and
dynamic loads imposed by heavy weather.
Have the ability to control the PTC through the air-sea interface at sufficient
speed to avoid excessive wave action.
Keep the PTC clear of the superstructure of the surface-support platform to
avoid impact damage.
Have lifting capability of sufficient power to permit fast retrieval of the PTC,
and controls and brakes that permit precision control for PTC mating and
approach to the seafloor.
Include a handling system to move the suspended PTC to and from the launch/
retrieval position to the DDC.
Have a method of restraining PTC movement during mating to the DDC.
Saturation Mixed-Gas Diving Equipment.
The UBA MK 21 MOD 0 is an open
circuit, demand-regulated diving helmet designed for saturation, mixed-gas diving
at depths in excess of 300 fsw and as deep as 950 fsw (Figure 15-2). With the
exception of the demand regulator, it is functionally identical to the UBA MK 21
MOD 1, which is used for air and mixed-gas diving. The regulator for the MK 21
MOD 0 helmet is the Ultraflow 500, which provides improved breathing resis-
tance and gas flow over the MK 21 MOD 1.
The UBA MK 22 MOD 0 is an open circuit, demand-regulated, band-mask
version of the UBA MK 21 MOD 0 (Figure 15-3). It is used for the standby diver
for saturation, mixed-gas diving at depths in excess of 300 fsw and as deep as 950
fsw. It is provided with a hood and head harness instead of the helmet shell to
present a smaller profile for storage.
Navy Experimental Diving Unit (NEDU), Panama City, FL.
NEDU’s mission is to
test and evaluate diving, hyperbaric, and other life-support systems and proce-
dures, and to conduct research and development in biomedical and environmental
physiology. NEDU then provides technical recommendations to Commander,
Naval Sea Systems Command to support operational requirements of our the U.S.
Armed Forces.
NEDU houses the Ocean Simulation Facility (OSF), one of the world’s largest
man-rated hyperbaric facilities. The OSF consists of five chambers with a wet pot
and transfer trunk. The wet pot holds 55,000 gallons of water. The OSF can simu-
late depths to 2,250 fsw and can accommodate a wide range of experiments in its
dry and wet chambers (see Figure 15-4, Figure 15-5, and Figure 15-6).
15-6 U.S. Navy Diving Manual—Volume 3
Naval Submarine Medical Research Laboratory (NSMRL), New London, CT.
mission of the Naval Submarine Medical Research Laboratory is to conduct
medical research and development in the fields of hyperbaric physiology, opera-
tional psychology and physiology, human factors engineering, and other allied
sciences as they apply to biomedical programs in operational environments
(Figure 15-7).
Saturation diver life-support systems must provide adequate respiratory and
thermal protection to allow work in the water at extreme depths and temperatures.
Because of the increased stresses placed upon the diver by deep saturation dives,
this equipment must be carefully designed and tested in its operating environment.
The diver life-support system consists of two components: an underwater
breathing apparatus (UBA) and a thermal protection system. The actual in-water
time a diver can work effectively depends on the adequacy of his life-support
apparatus and his physical conditioning. Important considerations in the duration
of effective in-water time are the rate of gas consumption for the system and the
degree of thermal protection. Present U.S. Navy saturation diving UBAs are
designed to operate effectively underwater for at least 4 hours. Although a given
diving apparatus may be able to provide longer diver life support, experience has
Figure 15-2.
MK 21 MOD 0 with Hot
Water Suit, Hot Water Shroud, and Come-
Home Bottle.
Figure 15-3.
MK 22 MOD 0 with Hot
Water Suit, Hot Water Shroud, and Come-
Home Bottle.
CHAPTER 15 — Saturation Diving 15-7
Figure 15-4.
NEDU’s Ocean Simulation Facility (OSF).
Figure 15-5.
NEDU’s Ocean Simulation Facility Saturation Diving Chamber Complex.
15-8 U.S. Navy Diving Manual—Volume 3
Figure 15-6.
NEDU’s Ocean Simulation Facility Control Room.
Figure 15-7.
Naval Submarine Medical Research Library (NSMRL).
CHAPTER 15 — Saturation Diving 15-9
shown that cumulative dive time at deep depths will progressively reduce diver
effectiveness after a 4-hour in-water exposure.
All saturation diver life-support systems include diver thermal protection
consisting of a hot water suit and a breathing gas heater. The thermal protection is
designed to minimize the divers heat loss caused by helium’s high thermal
conductivity. Helium conducts heat away from the body rapidly and causes a
significant heat loss via the divers breathing gas. The divers metabolic rate may
not be great enough to compensate for the heat loss when breathing cold gas,
resulting in a drop in body temperature and increasing the chance of hypothermia.
Diver Heating.
Because of the high thermal conductivity of helium and depths
attained, most conventional diving suits (i.e., wet suits/dry suits) provide inade-
quate insulation in a helium environment. As a result, thermal protection garments
for helium-oxygen saturation diving must employ active heating. The most
successful thermal protection currently used is the non-return valve (NRV) hot
water suit using circulating hot water as the heat source. The typical NRV hot
water suit is constructed from closed-cell, pre-crushed neoprene with an outer
layer of tough canvas-type nylon. The interior is lined with a softer nylon with
perforated hot water hoses along the limbs, chest, and backbone. Divers are
required to wear Polartec Diveskins or Neoprene liners under their NRV suits. The
liners or Diveskins offer almost no protection from cold water. The liners or Dive-
skins keep the divers from getting burned by hot water discharge from the NRV
suit and minimize chafing of skin.
The effectiveness of the hot water suit in keeping the divers warm is dependent
upon maintaining an adequate flow of water at the proper temperature. A 4-gallon
per minute (gpm) (3 gpm to the suit and 1 gpm to the breathing gas heater) hot
water flow rate with the suit inlet temperature adjusted to divers comfort gener-
ally provides adequate protection. During normal operation, hot water is
distributed through the NRV hot water suit and is then discharged to the sea
through the NRV. If there is a diver heating system failure, the diver shuts the
NRV and opens the bypass valve, trapping sufficient hot water in the suit to allow
him to return to the PTC. To prevent burn injury to the diver, the water tempera-
ture at the suit inlet should not exceed 110°F. Hot water thermal protection
systems should be designed to provide individual control of water temperature and
rate of flow supplied to each diver. All divers normally use umbilicals of similar
Inspired Gas Heating.
The thermal protection system includes a breathing-gas
heater to warm the gas to a temperature sufficient to minimize respiratory heat
loss. A typical breathing-gas heater is a hot water heat exchanger that can raise the
breathing-gas temperature by 30–50°F. Breathing cold helium-oxygen at deep
saturation diving depths can cause incapacitating nasal and trachea-bronchial
secretions, breathing difficulties, chest pain, headache, and severe shivering.
These symptoms may begin within minutes of starting the dive excursion.
15-10 U.S. Navy Diving Manual—Volume 3
Breathing apparently comfortable but low-temperature helium-oxygen at deep
depths can rapidly lower body temperature through respiratory heat loss, even
though the skin is kept warm by the hot water suit. The diver usually remains
unaware of respiratory heat loss, has no symptoms, and will not begin to shiver
until his core temperature has fallen. Metabolic heat production may not compen-
sate for continuing respiratory heat loss. Table 15-1 contains guidelines for the
minimum allowable temperatures for helium-oxygen breathing gas. These limits
are based on a 4-hour excursion with a maximum core body temperature drop of
1.8°F (1.0°C) in a diver wearing a properly fitted and functioning NRV or hot
water suit.
The rate of gas consumption and the composition of the gas supply depend in part
upon the design of the UBA. Three types of underwater breathing apparatus have
been used successfully to support saturation diving operations: demand open-
circuit, semiclosed-circuit, and closed-circuit.
UBA systems should be designed to support saturation diving excursions of at
least 4 hours duration in temperatures as low as 29°F. Specific information on
Table 15-1. Guidelines for Minimum Inspired HeO
Temperatures for Saturation
Depths Between 350 and 1,500 fsw.
Minimum Inspired Gas Temperature
Depth (fsw) °C °F
350 -3.1 26.4
400 1.2 34.2
500 7.5 45.5
600 11.7 53.1
700 14.9 58.8
800 17.3 63.1
900 19.2 66.6
1000 20.7 69.3
1100 22.0 71.6
1200 23.0 73.4
1300 23.9 75.0
1400 24.7 76.5
1500 25.4 77.72
* Ref: C. A. Piantadosi, “Respiratory Heat Loss Limits in Helium Oxy
en Saturation Divin
,” Navy
Experimental Divin
Unit Report NR 10-80 Revised 1982 (ADA 094132).
CHAPTER 15 — Saturation Diving 15-11
U.S. Navy certified diving equipment can be found in the applicable system-
specific technical manuals.
Gas usage can be the controlling factor in the planning for a mission and deter-
mining appropriate excursions. However, gas usage is UBA- and platform-
Specific Dives.
For a specific dive, storage of gas to support the mission may be
the controlling parameter. The following formulas may be used to calculate gas
usage by divers:
scfm (for one diver at depth) = ata × acfm
total scfm = scfm × number of divers
scf required = scfm × minutes
D = depth of diver
ata = atmosphere absolute
acfm = actual cubic feet per minute required by specific UBA being used (refer to
the tech manual)
number of divers = total number of divers making excursion
minutes = duration of excursion
scf required = standard cubic feet of gas required to support the divers
Two divers and one standby diver using the MK 21 MOD 0 and MK 22
MOD 0 UBAs at 300 fsw are deployed for a 15-minute excursion. Determine the
gas usage.
Convert the depth to atmospheres:
300 fsw 33 fsw+
33 fsw
10.09 ata=
15-12 U.S. Navy Diving Manual—Volume 3
Calculate gas usage for 1 diver:
Calculate gas usage for 3 divers:
Calculate the total gas usage requirement:
A gas usage requirement of 636 Standard Cubic Feet of helium-oxygen can be
expected for this two-diver excursion.
e for three divers is computed even thou
h the standby would not
normally be usin
as for the entire 15 minutes.
Emergency Gas Supply Duration.
The gas computation in paragraph 15-8.1 is
used to determine excursion limits based on divers gas storage. The diver’s emer-
gency gas supply (EGS) duration should also be calculated using the following
mmp = (D × .445) + psi (obp)
psi available for use = psi (cylinder) - mmp
scfm = acfm × ata
duration in minutes =
D = depth of diver
psi (obp) = over-bottom pressure required for specific UBA
mmp = minimum manifold pressure
10.09 ata
x 1.4 acfm for MK21 MOD 0
14.13 scfm for 1 diver at 300 fsw
14.13 scfm for 1 diver at 300 fsw
x 3 divers (2) and standby (1)
42.39 scfm for 3 divers at 300 fsw
42.39 scfm
x 15 minutes excursion time
635.85 scf (round up to 636 scf)
scf gas available
psi Available
CHAPTER 15 — Saturation Diving 15-13
fv = floodable volume of cylinder
acfm = actual cubic feet per minute at excursion depth required by specific UBA
being used
scfm = standard cubic feet per minute required to deliver acfm
Using an 80-cubic-foot aluminum cylinder (floodable volume = .399
cu. ft.) filled to 3,000 psig, calculate the diver’s EGS duration at 300 fsw.
Calculate the psi available for use:
Calculate the psig available for use:
3,000 - 319 psig = 2,681 psig available for use
Calculate the scf of gas available:
Calculate the standard cubic feet per minute required:
1.4 acfm
10.09 ata = 14.13 scfm
Calculate the duration of the gas supply:
The duration of the emergency gas supply is very short, especially at greater
Gas Composition.
The percentage of oxygen in the mix depends on diver depth
and can be calculated as follows:
% decimal equivalent =
% decimal equivalent × 100 = % of O
required to maintain desired ppO
Calculate the minimum and maximum percentage of O
required to
sustain a .44 to 1.25 ppO
range at 300 fsw.
185.0 overbottom psi, MK 21 MOD 0
+ 133.5 psi (300 fsw converted to psi)
318.5 psi (round up to 319 psi)
2681 14.7+
73.2 scf of gas available=
73.2 scf
14.13 scfm
5.18 minutes=
15-14 U.S. Navy Diving Manual—Volume 3
Calculate the minimum percentage of O
required to sustain the lower value of
the range:
4.36% O
in He provides the minimum ppO
Calculate the maximum percentage of O
required to sustain the lower value
of the range:
12.39% O
in He provides the maximum ppO
Saturation diving is the mode of choice for diving operations requiring long
bottom times or diving operations deeper than surface-supplied tables permit.
Saturation diving allows divers to remain at working depths without concern for
decompression. The Unlimited Duration Excursion Tables (Table 15-7 and Table
15-8) allow a large vertical range of working depths without time limits.
Saturation diving requires complex saturation diving systems designed to
precisely control depth, atmosphere composition, and temperature. Commanding
Officers, Diving Officers, and Master Divers must consider personnel and training
requirements, the physiological stress imposed by depth and dive duration, logis-
tics, and gas supply requirements. Refer to Table 15-2 for the personnel
requirements for saturation diving.
Dive Team Selection.
All candidates for a saturation dive shall be physically
qualified to make the dive as determined by a Saturation Diving Medical Officer.
With the exceptions of authorized research, testing of equipment, or training
purposes, all divers shall be qualified and experienced with the UBA being used
and in the particular dive system to which they are assigned. Depending on
mission requirements, divers may need to have special skills that are required for
the operation.
Mission Training.
When the schedule permits, training in preparation for a
specific saturation diving mission shall be conducted. This training provides an
opportunity to ensure that all personnel are in optimal physical condition and facil-
itates the development of special skills required for the operation. Training also
provides an opportunity for individuals to function as a team and to identify an
0.44 ata
10.09 ata
0.0436 100
1.25 ata
10.09 ata
0.1239 100
CHAPTER 15 — Saturation Diving 15-15
individual with leadership skills necessary to fill the role of dive team leader.
Alternate divers should be identified and trained with the team in the event of
illness or injury to a primary diver.
The selection of the storage depth for the deck decompression chamber (DDC) is
based on the approximate planned diver working depth. This can be achieved by
comparing the storage depth and planned diver working depth with the descent
and ascent limits of the Unlimited Duration Excursion Tables (Table 15-7 and
Table 15-8). When the diver’s working depth range is small, the DDC should be
compressed to approximately the middle of the range. This minimizes the amount
of gas used in pressurizing or depressurizing the personnel transfer capsule (PTC).
When the expected diver work range is large or multiple objectives at different
depths are to be accomplished, several different storage depths will be required.
The unlimited excursion procedures may be used at several progressively shal-
lower storage depths to accomplish the objective.
Table 15-2. Personnel Requirements for Saturation Diving.
Deep Diving System DDS MK 2 MOD 1 Dive Team
Watch Station NOBC/NEC (Note 1)
Officer 9315, 5346
Medical Officer (Note 2) 0107
Master Diver 5346
Supervisor 5311, 5346
Atmosphere Monitor 5346, 5311, 8493, 8494
MCC Gas-Control Operator 5311, 5342, 5346, 8493, 8493, 8494
Life-Support Operator 5311, 5342, 5346, 8493, 8494
MCC Communications and Lo
Operator 5311, 5342, 8493, 5343, 5346, 8494
Surface-Support Divers 5311, 5342, 8493, 5343, 5346, 8494
Gas Kin
5346, 5311, 8493, 5342, 8494
PTC Operators 9315, 5346, 5311, 8493, 8494
PTC Divers 9315, 5346, 5311, 8493, 8494
Main Deck Supervisors 5346, 5311, 5342
1. The NECs listed are the minimum level qualifications allowed. The surface-support divers must
be qualified in the divin
method bein
used. NOBC 9135 and NEC 5346 can stand any watch
for which qualified except Divin
Medical Officer. NEC 5311 can qualify to stand Dive Watch
Supervisor. Mannin
is shown for use of one DDC only. Additional handlin
crew for the PTC is
required from ship’s personnel, but the PTC handlin
crew is not shown on the chart.
2. A Divin
Medical Officer is required on site for all saturation divin
operations. (“On site” is
defined as accessible within 30 minutes of the dive site by available transportation.)
15-16 U.S. Navy Diving Manual—Volume 3
This section covers the records required to be maintained during the conduct of a
saturation dive.
Command Diving Log.
An official diving log shall be maintained at all times
throughout the dive. It shall contain a chronological record of the dive procedure
in addition to any significant events. A narrative of significant events is to be
recorded by the Diving Officer (or Diving Supervisor) and Saturation Diving
Medical Officer (as necessary). This log shall be retained for 3 years.
Master Protocol.
Each diving operation shall have a master protocol submitted by
the Master Diver, reviewed by the Saturation Diving Medical Officer and Diving
Officer, and approved by the Commanding Officer. This master protocol shall
contain all the information needed to ensure that the dive follows a program
consistent with the requirements for saturation diving as defined in this manual
and shall include the necessary information to carry out these procedures on the
specific operational platform.
A copy of the protocol shall be maintained as the master copy at the MCC. No
alterations except those made by the Diving Officer and approved by the
Commanding Officer are permitted. Any changes to this protocol shall be signed
and dated.
Because saturation dives generally follow a predictable pattern,
only a few elements of protocol need to be modified from mission to mission.
Consequently, once a complete and carefully written protocol is available, only
minor modifications will be needed to support future missions.
The dive protocol shall include, but is not limited to, the following:
A detailed gas-usage plan, including projected gas supply requirements (para-
graph 15-15). The required mixtures for supplying emergency, treatment, and
excursion gas shall be specified for the depth ranges expected with specific
depths to shift mixes indicated.
A compression schedule, including planned rate of travel with rest stops, if
Manning requirements, including a watchbill.
Predive and postdive procedures.
Chamber Atmosphere Data Sheet.
Hourly readings of chamber pressure, temper-
ature, humidity, oxygen, and carbon dioxide concentrations shall be recorded. In
addition, time of operation of the carbon dioxide scrubbers and time of carbon
dioxide absorbent replenishment shall be recorded.
CHAPTER 15 — Saturation Diving 15-17
Service Lock.
The following information shall be recorded: date, depth, clock
time upon leaving the surface or leaving the bottom, and items locked in or out of
the chamber. This information is useful in controlling the spread of contaminants
and in minimizing the combustibles in the chamber while in the fire zone.
Machinery Log/Gas Status Report.
A record of the status of all gas banks,
including their pressure and mixture, and of the status of all DDS gas delivery
equipment, shall be maintained. This log shall be reviewed by each oncoming
Diving Supervisor prior to assuming the watch and daily by the Diving Officer
and Master Diver.
Operational Procedures (OPs).
Currently approved operational procedure sheets
are to be properly completed and signed by the operator and then reviewed and
signed by the Diving Supervisor and Dive Watch Officer and logged in the
Command Smooth Log.
Emergency Procedures (EPs).
A set of approved emergency procedures with
each individual watch station’s responsibilities shall be separately bound and
available at the main control console throughout a saturation dive. The conve-
nience of having emergency procedures on station does not relieve any diver or
any saturation diving watch team member from being sufficiently knowledgeable,
thoroughly trained, and fully qualified to react efficiently and instantaneously to
any emergency. Constant training in these emergency procedures is necessary to
maintain watchstanding proficiency.
Individual Dive Record.
Use the Dive Reporting System (DRS) to record and
report dives, as outlined in paragraph 5-9.
In planning an extended diving operation, care must be taken to ensure that suffi-
cient supplies and power to support a diving mission are available. When
operating at remote sites, the Commanding Officer and Diving Officer must care-
fully evaluate the availability of shore-based support. Loss of steam and/or
electrical power at sea is an emergency situation. The loss of either of these vital
services to the saturation dive system with a dive team committed to lengthy
decompression constitutes a major emergency that must be acted upon quickly.
Accordingly, transit times and contingency plans must be made prior to
commencing saturation diving operations at remote sites in case support services
for the dive complex are threatened or lost.
15-18 U.S. Navy Diving Manual—Volume 3
The hyperbaric atmosphere within the DDC and PTC is controlled to maintain the
gaseous components as follows:
Oxygen levels and time limits are presented in Table 15-3.
These levels, particularly that of oxygen, are essential for safe decompression and
the use of the Unlimited Duration Excursion Tables. Increases in the oxygen
partial pressure above 0.6 ata for extended periods (greater than 24 hours) risk
pulmonary oxygen toxicity and should only be used in emergency situations. A
below 0.42 ata may result in inadequate decompression, and a ppO
0.16 ata will result in hypoxia. Once carbon dioxide concentration reaches 0.5
percent surface equivalent (3.8 millimeters of mercury) for 1 hour, the scrubber
canister should be changed, because carbon dioxide levels tend to rise rapidly
thereafter. An inspired carbon dioxide level of 2 percent surface equivalent (15.2
millimeters of mercury) can be tolerated for periods of up to 4 hours at depth.
Nitrogen concentration tends to decrease with time at depth, due to purging by
helium during service lock operation.
NOTE Dischar
as into the PTC durin
operations may make it
difficult to control the oxy
en level.
The following gases shall be available for use in a UBA, for emergency supply,
and for the treatment of decompression sickness.
en Partial Pressure .44 – .48 ata
Carbon Dioxide Partial Pressure Less than 0.005 ppCO
(.5% SEV) (3.8 millimeters of mercury)
Helium and Nitro
en Balance of total pressure
Table 15-3. Chamber Oxygen Exposure Time Limits.
Oxygen Level (ata) Time
e .44 – .48 Unlimited
Excursion .40 – .60 4 hours (6 hours)***
Excursion associated with
.42 – .48* Unlimited
ency .60** 24 hours
* This level may be exceeded prior to startin
the upward excursion for decompression.
** If oxy
en levels exceed this limit, switch to emer
*** Diver performance exponentially decreases between 4 and 6 hours of an in-water excursion.
CHAPTER 15 — Saturation Diving 15-19
UBA Gas.
An adequate quantity of gas within an oxygen partial pressure range of
0.44–1.25 ata shall be available for use.
Emergency Gas.
Emergency gas is used as a backup breathing supply in the event
of DDC or PTC atmosphere contamination. An emergency gas with an oxygen
partial pressure of 0.16 to 1.25 ata shall be immediately available to the built-in
breathing system (BIBS). The volume of emergency breathing gas shall be suffi-
cient to supply the divers for the time needed to correct the DDC atmosphere.
Upward excursions of the PTC or DDC or decompression shall not be started
during emergency gas breathing unless the oxygen partial pressure of the diver’s
inspired gas is 0.42 ata or above.
An emergency gas schedule for a dive beyond 850 fsw is:
Treatment Gases. .
Treatment gases having an oxygen partial pressure range of
1.5 to 2.8 shall be available in the event of decompression sickness. The premixed
gases shown in Table 15-4 may be used over the depth range of 0 – 1,600 fsw. A
source of treatment gas shall be available as soon as treatment depth is reached.
The source shall be able to supply a sufficient volume of breathing gas to treat
each chamber occupant.
Helium-oxygen gas mixtures conduct heat away from the diver very rapidly. As a
result, temperatures higher than those required in an air environment are necessary
to keep a diver comfortable. As depth increases, the temperature necessary to
achieve comfort may increase to the 85–93°F range.
Bank Mix
#1 84/16 HeO
#2 96/4 HeO
Allowable Depth Ran
e (fsw)
Shift Depth (fsw)
Table 15-4. Treatment Gases.
Depth (fsw) Mix
0–60 100% O
60–100 40/60% HeO
100–200 64/36% HeO
200–350 79/21% HeO
350–600 87/13% HeO
600–1000 92/08% HeO
1000–1600 95/05% HeO
15-20 U.S. Navy Diving Manual—Volume 3
As a general guideline to achieve optimum comfort for all divers, the temperature
should be kept low enough for the warmest diver to be comfortable. Cooler divers
can add clothing as needed. All divers should be questioned frequently about their
The relative humidity should be maintained between 30 and 80 percent with 50 to
70 percent being the most desirable range for diver comfort, carbon dioxide
scrubber performance, and fire protection.
Every effort shall be made to eliminate any fire hazard within a chamber. When
oxygen percentages are elevated as during the later stages of decompression, a fire
will burn rapidly once started, perhaps uncontrollably. As a result, special precau-
tions are necessary to protect the divers safety when in the fire zone. The fire zone
is where the oxygen concentration in the chamber is 6 percent or greater. Using
standard saturation diving procedures (oxygen partial pressure between 0.44 and
0.48 ata), fire is possible at depths less than 231 fsw. Thus, during a saturation
dive the divers will be in the fire zone during initial compression to depth and
during the final stages of decompression.
The chamber atmosphere is 0.48 ata ppO
. The minimum oxygen
percentage for combustion is 6 percent. Compute the fire zone depth.
The fire zone depth is computed as follows:
Although the design of the DDS minimizes fire potential, personnel must remain
vigilant at all times to prevent fires. Appropriate precautions for fire prevention
Fire-suppression systems, if available, must be operational at all times when in
the fire zone.
Chamber clothing, bed linen, and towels shall be made of 100% cotton. Diver
swim trunks made of a 65% polyester–35% cotton material is acceptable.
Mattresses and pillows shall be made of fire-retardant material when in the fire
Limit combustible personal effects to essential items.
Limit reading material, notebooks, etc., in the fire zone.
Fire zone depth (fsw)
0.48 33
231 fsw=
CHAPTER 15 — Saturation Diving 15-21
All potential combustibles shall be locked in only with the permission of the
Diving Supervisor.
Whenever possible, stow all combustibles, including trash, in fire-retardant
containers, and lock out trash as soon as possible.
Being thoroughly familiar with all emergency procedures (EPs) regarding fire
inside and outside the Deep Diving System.
Once a saturation dive begins, any illness that develops is likely to affect the entire
team, reducing their efficiency and perhaps requiring the dive to be aborted. To
minimize this possibility, the Saturation Diving Medical Officer should conduct a
brief review of the divers physical condition within 24 hours of compression. If
an infectious process or illness is suspected, it shall be carefully evaluated by the
Saturation Diving Medical Officer for possible replacement of the diver with a
previously designated alternate diver. Strict attention to personal hygiene,
chamber cleanliness, and food-handling procedures should be maintained once the
dive begins to minimize the development and spread of infection.
Personal Hygiene.
Personal hygiene and cleanliness is the most important factor
in preventing infections, especially skin and ear infections. All divers should wash
at least daily, and as soon as possible after wet excursions. Fresh linens and
clothing should be locked into the complex every day. To prevent foot injury,
clean, dry footwear should be worn at all times except while showering, sleeping,
or in diving dress. Feet must be thoroughly dry, especially between the toes, to
minimize local infections. A personal toiletry bag shall be maintained by each
chamber occupant. These bags shall be inspected by the Diving Supervisor or
Master Diver prior to commencing the dive to prevent potential contaminants or
fire hazards from being carried into the chamber.
Prevention of External Ear Infections.
Severe ear infections can develop unless
preventative measures are taken. An effective preventative regime includes irri-
gating each ear with 2 percent acetic acid in aluminum acetate solution (i.e.,
DOMEBORO) for 5 minutes at least twice daily. Irrigation shall be observed by
the Diving Supervisor, timed by the clock, and logged.
After a week or so, even with the ear prophylaxis regimen, the ear canals may
become occluded with debris. Once this happens, an ear infection may develop
rapidly. In order to prevent this occurrence, all divers should be trained to detect
and treat blockage. Before beginning a dive, all divers should be trained by quali-
fied medical personnel to use an otoscope to view the ear drum. Also, they should
be trained to use an ear syringe. At least weekly during a dive, divers should
examine each other’s ear canals. If the ear drum cannot be viewed because of a
blockage, then the canal should be gently irrigated with the ear syringe until the
canal is unplugged.
15-22 U.S. Navy Diving Manual—Volume 3
Chamber Cleanliness.
Strict attention shall be paid to chamber cleanliness at all
times, particularly in the area of the toilet, wash basin, shower, and service locks.
Only approved compounds shall be used to clean the chamber, components, and
clothing used in the pressurized environment. During wet excursions, close atten-
tion shall be paid to routine postdive cleaning of the diver-worn equipment to
prevent rashes and skin infections.
Upon completing a saturation dive, the chamber should be well ventilated,
emptied, and liberally washed down with non-ionic detergent (MIL-D-16791) and
water and then closed. Additionally, all chamber bedding, linens, and clothing
shall be washed.
Food Preparation and Handling.
All food provided to the divers during a satura-
tion diving evolution shall meet the standards prescribed in NAVMED P-5010.
All food locked in shall be inspected by the Dive Watch Supervisor or Dive Watch
Officer. The Saturation Diving Medical Officer should inspect food preparation
areas daily.
Preventing chamber atmosphere contamination by toxic gases is extremely impor-
tant to the health of the divers. Once introduced into the chambers, gaseous
contaminants are difficult to remove and may result in prolonged diver exposure.
Gaseous Contaminants.
Gaseous contaminants can be introduced into the
chamber through a contaminated gas supply, through chamber piping and/or gas
flasks containing residual lubricants or solvents, or by the divers or maintenance
The hazard of atmospheric contamination can be reduced by ensuring that only
gases that meet the appropriate federal specifications are used and that appropriate
gas transfer procedures are used. All gas flasks and chamber piping used with
helium, oxygen, or mixed gases shall be cleaned using approved cleaning proce-
dures to remove substances that may become chamber contaminants. Once
cleaned, care shall be taken to prevent introduction of contaminants back into
these systems during maintenance by marking and bagging openings into the
piping system. Finally, inadvertent chamber contamination can be prevented by
limiting the items that may be taken inside. Only approved paints, lubricants,
solvents, glues, equipment, and other materials known not to off-gas potential
toxic contaminants are allowed in the chamber. Strict control of all substances
entering the chamber is an essential element in preventing chamber contamination.
Initial Unmanned Screening Procedures.
To ensure that chamber systems are
free of gaseous contaminants, the chamber atmosphere shall be screened for the
presence of the common contaminants found in hyperbaric systems when contam-
ination of the chamber and/or gas supply is suspected, or after any major chamber
repair or overhaul has been completed. Only NAVFAC- or NAVSEA-approved
procedures may be used to collect screening samples.
CHAPTER 15 — Saturation Diving 15-23
Table 15-5 lists a few selected contaminants that may be present in hyperbaric
complexes, with their 90-day continuous exposure limits (or 7-day limits where a
90-day limit is not available). In the absence of specific guidelines for hyperbaric
exposures, these limits shall be used as safe limits for saturation diving systems.
When any one of these contaminants is reported in chamber samples, the calcu-
lated Surface Equivalent Value (SEV) shall be compared to the limit on this list. If
the calculated SEV exceeds this limit, the chamber shall be cleaned and retested.
Assistance with any contamination identification and resolution can be obtained
by contacting NEDU or the system certification authority for guidance.
Table 15-5. Limits for Selected Gaseous Contaminants in Saturation Diving Systems.
Contaminant Limit
Acetone 200 ppm (Note 1) (Note 3: Same limit)
Benzene 1 ppm (Note 3)
Chloroform 1 ppm (Note 1)
Ethanol 100 ppm (Note 3)
Freon 113 100 ppm (Note 1)
Freon 11 100 ppm (Note 1)
Freon 12 100 ppm (Note 1) (Note 3: Same limit)
Freon 114 100 ppm (Note 1)
Isopropyl Alcohol 1 ppm (Note 1)
Methanol 10 ppm (Note 3)
Methyl Chloroform 30 ppm (Note 2) (Note 3: 90-day limit = 2.5
ppm, 24-hour limit = 10 ppm)
Methyl Ethyl Ketone 20 ppm (Note 2)
Methyl Isobutyl Ketone 20 ppm (Note 2)
Methylene Chloride 25 ppm (Note 2)
Toulene 20 ppm (Note 1) (Note 3: Same limit)
Trimethyl Benzenes 3 ppm (Note 2)
Xylenes 50 ppm (Note 1) (Note 3: Same limit)
1. 90-day continuous exposure limit.
National Research Council Committee on Toxicology
Emergency and Continuous Exposure Limits for Selected Airborne Contaminants
, Vols. 1-8,
ton, D.C., National Academy Press, 1984–1988.
2. 7-day maximum allowable concentration in manned spacecraft. National Aeronautics and
Space Administration, Office of Space Transportation Systems.
Flammability, Odor, and
Offgassing Requirements and Test Procedures for Materials in Environments that Support
, NHB 8060, 1B, Washin
ton, D.C., U.S. Government Printin
Office, 1981.
3. 90-day limit.
U.S. Naval Sea Systems Command Nuclear Powered Submarine Atmosphere
Control Manual
, NAVSEA S9510-AB-ATM-010 (U), Vol. 1, Revision 2, 30 July 1992.
15-24 U.S. Navy Diving Manual—Volume 3
The initial phase of the dive is the compression of the dive team to the selected
storage depth. This phase includes establishing the chamber oxygen partial pres-
sure at a value between 0.44 and 0.48 ata, instrument and systems checkouts, and
the actual compression of the divers to storage depth.
Establishing Chamber Oxygen Partial Pressure.
Prior to compression to storage
depth, the chamber oxygen partial pressure shall be raised from 0.21 ata to 0.44–
0.48 ata. There are two methods of raising the oxygen partial pressure to the
desired level.
Air Method
. Compress the chamber with air at a moderate rate to 36 fsw. This
will raise the chamber ppO
to 0.44 ata. If desired, further elevation of the
chamber ppO
to 0.48 ata can be undertaken by using the oxygen makeup
Helium-Oxygen Method
. Compress the chamber at a moderate rate with a
helium-oxygen mixture containing less than 21 percent oxygen. The depth of
the required compression can be calculated using the following formula:
If a 20 percent mixture of helium-oxygen is used and the desired ppO
is 0.44 ata, calculate the compression depth.
Compression to Storage Depth.
Rapid compression to saturation storage depth
may provoke symptoms of High-Pressure Nervous Syndrome (HPNS) and may
intensify compression joint pains. To avoid these complications, the slowest rate
of compression consistent with operational requirements should be used. Table
15-6 shows the range of allowable compression rates.
Table 15-6. Saturation Diving Compression Rates.
Depth Range Compression Rate
0–60 fsw 0.5 – 30 fsw/min
60–250 fsw 0.5 – 10 fsw/min
250–750 fsw 0.5 – 3 fsw/min
750–1000 fsw 0.5 – 2 fsw/min
Compression Depth (fsw) 33
Compression depth 33
0.44 0.21
37.95 fsw=
CHAPTER 15 — Saturation Diving 15-25
If operational necessity dictates, compression to storage depth of 400 fsw or shal-
lower can be made at the maximum rates indicated in Table 15-6 with little risk of
HPNS. Direct compression at maximum rates to deeper storage depths, however,
may produce symptoms of HPNS in some divers. These divers may be unable to
perform effectively for a period of 24 to 48 hours. Experience has shown that the
appearance of such symptoms can be minimized by slowing compression rates or
introducing holds during compression.
The depth and time duration of holds, if used, may be adjusted to suit operational
requirements and diver comfort.
Precautions During Compression.
During compression the chamber atmosphere
shall be monitored carefully. The chamber atmosphere may not mix well during
rapid compression, resulting in areas of low oxygen concentration.
Abort Procedures During Compression.
The following abort procedure is
authorized if a casualty occurs during compression. Consult with a Saturation
Diving Medical Officer prior to committing to this procedure. This procedure is
normally used for shallow aborts where the maximum depth and bottom time do
not exceed the limits of the table.
Using the Surface Supplied HeO
Tables, the following procedure applies:
. Use the actual chamber depth.
Bottom Time
. If the initial compression uses air, time spent shallower than 40
fsw, up to a maximum of 60 minutes, is not counted as bottom time. If the ini-
tial compression uses helium, time starts when leaving the surface.
. Maintain BIBS between 1.5 – 2.8 ppO
. Follow the scheduled stops of the Surface Supplied HeO
. For every 25 minutes of breathing BIBS gas, take a 5-minute break
breathing a gas between 0.16 to 1.25 ata ppO
. The 5-minute break counts as a
stop time. The lower oxygen percentage shall not be less than 0.16 ata ppO
Upon completing abort decompression, all divers shall be closely monitored and
observed for a minimum of 24 hours. For deeper emergency aborts beyond the
limits of the Surface-supplied HeO
Tables, refer to paragraph 15-23.7.2.
The Unlimited Duration Excursion Tables (Table 15-7 and Table 15-8) allow
multiple diver excursions to be conducted during the course of a saturation dive.
When using these excursion procedures, the diving supervisor need only be
concerned with the depth of the divers. To use these tables when planning the
dive, select a chamber storage depth in a range that allows diver excursions shal-
15-26 U.S. Navy Diving Manual—Volume 3
Table 15-7. Unlimited Duration Downward Excursion Limits.
Storage Depth
Distance (ft)
Depth (fsw)
Storage Depth
Distance (ft)
Depth (fsw)
10 33 43 410 106 516
20 37 57 420 107 527
30 40 70 430 108 538
40 43 83 440 109 549
50 46 96 450 111 561
60 48 108 460 112 572
70 51 121 470 113 583
80 53 133 480 114 594
90 56 146 490 115 605
100 58 158 500 116 616
110 60 170 510 117 627
120 62 182 520 118 638
130 64 194 530 119 649
140 66 206 540 120 660
150 68 218 550 122 672
160 70 230 560 123 683
170 72 242 570 124 694
180 73 253 580 125 705
190 75 265 590 126 716
200 77 277 600 127 727
210 78 288 610 128 738
220 80 300 620 129 749
230 82 312 630 130 760
240 83 323 640 131 771
250 85 335 650 132 782
260 86 346 660 133 793
270 88 358 670 133 803
280 89 369 680 134 814
290 90 380 690 135 825
300 92 392 700 136 836
310 93 403 710 137 847
320 95 415 720 138 858
330 96 426 730 139 869
340 97 437 740 140 880
350 98 448 750 141 891
360 100 460 760 142 902
370 101 471 770 143 913
380 102 482 780 144 924
390 103 493 790 144 934
400 105 505 800 145 945
810 146 956
820 147 967
830 148 978
840 149 989
850 150 1000
CHAPTER 15 — Saturation Diving 15-27
Table 15-8. Unlimited Duration Upward Excursion Limits.
Storage Depth
Distance (ft)
Depth (fsw)
Storage Depth
Distance (ft)
Depth (fsw)
510 105 405
29 29 0 520 106 414
30 29 1 530 107 423
40 32 8 540 108 432
50 35 15 550 110 440
60 37 23 560 111 449
70 40 30 570 112 458
80 42 38 580 113 467
90 44 46 590 114 476
100 47 53 600 115 485
110 49 61 610 116 494
120 51 69 620 117 503
130 53 77 630 118 512
140 55 85 640 119 521
150 56 94 650 119 531
160 58 102 660 120 540
170 60 110 670 121 549
180 62 118 680 122 558
190 63 127 690 123 567
200 65 135 700 124 576
210 67 143 710 125 585
220 68 152 720 126 594
230 70 160 730 127 603
240 71 169 740 128 612
250 73 177 750 129 621
260 74 186 760 130 630
270 76 194 770 131 639
280 77 203 780 131 649
290 79 211 790 132 658
300 80 220 800 133 667
310 81 229 810 134 676
320 83 237 820 135 685
330 84 246 830 136 694
340 85 255 840 137 703
350 87 263 850 137 713
360 88 272 860 138 722
370 89 281 870 139 731
380 90 290 880 140 740
390 92 298 890 141 749
400 93 307 900 142 758
410 94 316 910 142 768
420 95 325 920 143 777
430 96 334 730 144 786
440 97 343 940 145 795
450 99 351 950 146 804
460 100 360 960 146 814
470 101 369 970 147 823
480 102 378 980 148 832
490 103 387 990 149 841
500 104 396 1000 150 850
15-28 U.S. Navy Diving Manual—Volume 3
lower or deeper than the storage depth. The actual depth of the work site or PTC
may be significantly different from the storage depth.
When using Table 15-8, enter the table at the deepest depth attained at any time
within the last 48 hours. While the DDC may be at 400 fsw, if one diver had
reached a depth of 460 fsw during an in-water excursion, the maximum upward
excursion depth for the divers is 360 fsw instead of 307 fsw. After completing
work at one depth and then compressing DDC to a deeper storage depth, unlimited
downward or upward excursions are permitted immediately upon reaching the
new storage depth. When decompressing the DDC from a deeper depth using stan-
dard saturation decompression procedures, unlimited downward excursions, as
defined in Table 15-7, may begin immediately upon reaching the new chamber
storage depth. A minimum of 48 hours shall elapse at the new storage depth before
any upward excursions may be made.
After decompression from 1,000 fsw to 400 fsw, the maximum
downward excursion is 105 fsw. After 48 hours have elapsed at 400 fsw, a full
upward excursion of 93 fsw to 307 fsw is permitted.
If less than 48 hours is spent at the new storage depth, the maximum upward
excursion is based on the deepest depth attained in the preceding 48 hours.
Decompression from a 1,000 fsw dive has been conducted to the 400
fsw depth. Twenty-four hours have been spent at 400 fsw. The dive log shows that
the deepest depth attained in the preceding 48 hours is 496 fsw. The maximum
upward excursion from Table 15-8, based on a 496 fsw depth, is to 396 fsw (500 –
104) allowing a maximum of a 4 fsw upward excursion. After 36 hours have
elapsed at 400 fsw, the dive log shows that the deepest depth attained in the
preceding 48 hours was 448 fsw. From Table 15-8, the shallowest excursion depth
is now 351 fsw.
The ascent rate should not exceed 60 fsw/min during an excursion. When it is
detected that a diver is ascending faster than 60 fsw/min, the diver shall immedi-
ately stop and wait until enough time has elapsed to return to the 60 fsw/min
schedule. The diver may then resume ascent at a rate not to exceed 60 fsw/min
from that depth.
If storage depth falls between the depths listed in Table 15-7, use the next shal-
lower depth (e.g., if the storage depth is 295 fsw, enter Table 15-7 at 290 fsw). If
storage depth falls between the depths listed in Table 15-8, use the next deeper
depth (e.g., if the storage depth is 295 fsw, enter Table 15-8 at 300 fsw).
Excursion Table Examples.
Example 1.
The chamber was compressed to 400 fsw from the surface. The initial
depth in Table 15-7 is 400 fsw. The maximum downward excursion for an
unlimited period not requiring decompression is 105 fsw, allowing a maximum
diver depth of 505 fsw. If the diver descends to 450 fsw, the maximum depth
achieved from the 400 fsw storage depth will be 450 fsw. Table 15-8 at 450 fsw
CHAPTER 15 — Saturation Diving 15-29
allows a 99 fsw upward excursion to a depth of 351 fsw. Thus, these divers may
move freely between the depths of 351 and 450 fsw while at a storage depth of 400
Example 2.
At a storage depth of 600 fsw, during which dives were made to 650
fsw, the maximum upward excursion that may by made to begin saturation
decompression is:
If less than 48 hours have elapsed since the 650 fsw excursion, Table 15-8
allows a maximum upward excursion of 119 fsw from a deepest depth of 650
fsw to a depth of 531 fsw.
If more than 48 hours have elapsed since the excursion, the maximum upward
excursion allowed is 115 fsw from 600 fsw to 485 fsw.
Example 3.
At the new shallower storage depth of 350 fsw, divers conduct an
excursion to 400 fsw. Using the deepest depth of 400 fsw achieved during storage
at 350 fsw, a maximum upward ascent from Table 15-8 of 93 fsw to a depth of 307
fsw is allowed, provided the chamber and the divers have been at the storage depth
of 350 fsw for at least 48 hours. Otherwise, no upward excursion is permitted.
PTC Diving Procedures.
Actual PTC diving operations are dictated by the Unit’s
operating instructions. In conducting these operations, experience indicates that a
maximum in-water time of 4 hours is optimal for diver efficiency. Longer dive
times result in a loss of diver effectiveness because of fatigue and exposure, while
shorter dives will significantly increase the time at depth for the completion of
operations. Standard practice is to rotate in-water divers with the PTC operators,
allowing two 4-hour dives to be conducted during a single PTC excursion to the
work site. Proper positioning of the PTC near the objective is important in
ensuring that the diver does not exceed the maximum permitted excursion limits
(Figure 15-8).
PTC Deployment Procedures.
A brief overview of PTC deployment procedures
For initial pressurization, the PTC, with internal hatch open, is usually mated
to the DDC. Divers enter the DDC and secure the hatches.
The DDC and PTC are pressurized to bottom depth. The divers transfer to the
PTC and secure the DDC and PTC hatches after them.
The trunk space is vented to the atmosphere and then the PTC is deployed and
lowered to working depth. The hatch is opened when seawater and internal
PTC pressures are equal. The divers don diving equipment and deploy from
the PTC.
Divers return to the PTC and secure the hatch. The PTC is raised and mated to
the DDC, and the divers transfer to the DDC. Until they are decompressed in
the DDC, the divers rotate between periods of living in the DDC and working
15-30 U.S. Navy Diving Manual—Volume 3
on the bottom. Deep underwater projects requiring moderate bottom time or
diver activities involving work at various depths are conducted in the
saturation mode with excursion dives. The PTC and DDC are pressurized to a
storage depth within the ascent and descent limits of the Unlimited Duration
Excursion Tables (Table 15-7 and Table 15-8), maximizing diving efficiency
for deep, long dives. Once tissue saturation is reached, decompression
requirements no longer increase.
Figure 15-8.
PTC Placement Relative to Excursion Limits.
CHAPTER 15 — Saturation Diving 15-31
Major DDS emergencies include loss of atmosphere control, loss of depth control
and fire in the DDC. Emergencies will be covered by locally prepared and
NAVSEA- or NAVFAC-approved emergency procedures. The following are
guidelines for establishing these procedures.
Loss of Chamber Atmosphere Control.
Loss of chamber atmosphere control
includes loss of oxygen control, high carbon dioxide level, chamber atmosphere
contamination and loss of temperature control.
Loss of Oxygen Control.
Divers can be safely exposed to chamber oxygen partial
pressures between 0.16 and 1.25 ata; however, efforts should be implemented
immediately to correct the problem and reestablish normal oxygen levels. For an
oxygen partial pressure from 0.16 to 0.48 ata, the normal oxygen addition system
can be used to increase the oxygen level slowly over time. For an oxygen partial
pressure above 0.48, it may be necessary to secure the oxygen addition system and
allow the divers to breathe down the chamber oxygen to a normal level. Table 15-3
lists the chamber oxygen exposure time limits. If these limits are exceeded, the
divers should be placed on BIBS and the chamber ventilated to reduce the oxygen
Loss of Carbon Dioxide Control.
When the DDC’s life-support system loses its
ability to absorb carbon dioxide, the level of carbon dioxide within the chamber
will rise at a rate depending on the chamber size and the combined carbon dioxide
production rate of the divers. An increasing carbon dioxide level may be the result
of exhaustion of the carbon dioxide absorbent or inadequate gas flow through the
carbon dioxide absorbent canister. If, after the carbon dioxide absorbent canister is
changed, chamber carbon dioxide level still cannot be brought under 0.005 ata (3.8
mmhg), the flow through the canister may be inadequate. Divers shall don BIBS
when the chamber carbon dioxide level exceeds 0.06 ata (45.6 mmhg).
Atmosphere Contamination.
If an abnormal odor is detected or if several divers
report symptoms of eye or lung irritation, coughing, headache, or impaired perfor-
mance, contamination of the chamber atmosphere should be suspected. The divers
shall be placed on BIBS and emergency procedures executed. The divers should
be isolated in the part of the complex thought to be least contaminated. Test the
chamber atmosphere using chemical detector tubes or by collecting a gas sample
for analysis on the surface, as described in paragraph 15-19.2. If atmosphere
contamination is found, the divers should be moved to the chamber or PTC with
the least level of contamination and this chamber isolated from the rest of the
Interpretation of the Analysis.
The allowable contaminant limits within a diving
system are based upon the Threshold Limit Values (TLV) for Chemical
Substances and Physical Agents guidelines published by the American Confer-
ence of Governmental Industrial Hygienists (ACGIH). TLVs are the time-
weighted average concentration for an 8-hour work day and a 40-hour work week,
to which nearly all workers can be repeatedly exposed day after day without
15-32 U.S. Navy Diving Manual—Volume 3
adverse effect. These guidelines are published yearly and should be used to deter-
mine acceptability. Because the partial pressure of a gas generally causes its
physiological effects, the published limits must be corrected for the expected
maximum operating depth (ata) of the diving system.
The solution to an atmosphere contamination problem centers around identifying
the source of contamination and correcting it. Gas samples from suspected sources
must be checked for contaminants. Special attention should be given to recently
changed and cleaned piping sections, gas hoses, and diver umbilicals, any of
which may contain residual cleaning solvents. Surfaced chambers should be thor-
oughly ventilated with air or a breathable helium-oxygen mixture (to prevent
hypoxia in maintenance personnel), inspected, and thoroughly scrubbed down to
remove residual contaminants. These chambers can then be compressed to depth
using a gas bank that is free of contaminants, the divers can be transferred to this
chamber, and the surface cleaning process can be repeated on the remaining
chamber(s). After cleaning and compression to depth, the chamber should be
checked periodically for recurrence of the contamination.
Loss of Temperature Control.
Loss of temperature control of more than 2–3°F
above or below the comfort level may lead to severe thermal stress in the divers.
Studies have shown that heat loss by perspiring is less effective in a hyperbaric
atmosphere. Heating a chamber to warm up cold divers may result in the divers
rapidly becoming overheated. Heat stroke may then become a possibility. The
potential for uncontrolled chamber heating occurs when chambers and PTCs are
exposed to direct sunlight.
When the chamber temperature falls, the divers begin intense shivering and hypo-
thermia develops unless rapid and aggressive measures are taken to correct the
problem. Divers may be provided with insulated clothing, blankets, and sleeping
bags. The best of these insulators are of limited effectiveness within the helium-
oxygen environment and will provide marginal protection until the problem can be
corrected. Special thermal protection systems have been designed for the use
within DDCs. These systems include thermal protection garments, insulating deck
pads or hammocks, and combination carbon dioxide absorbent and respiratory-
heat regenerator systems.
Loss of Depth Control.
Loss of depth control is defined as a pressure loss or gain
that cannot be controlled within the normal capabilities of the system. When loss
of depth control is encountered, all deployed divers shall be recovered immedi-
ately and all divers placed on BIBS. Attempt to control depth by exhausting excess
gas or adding helium to minimize depth loss until the cause can be found and
corrected. If the depth change is in excess of that allowed by the Unlimited Dura-
tion Excursion Tables, the divers should be returned to the original storage depth
immediately and the Diving Medical Officer notified.
Fire in the DDC.
Because fire within a DDC may progress rapidly, the divers and
watchstanders must immediately activate the fire suppression system and secure
the oxygen system as soon as a fire is suspected. When the fire suppression system
CHAPTER 15 — Saturation Diving 15-33
is activated, all divers shall immediately go on BIBS. Watchstanders should
monitor depth carefully because an extensive fire will cause an increase in depth.
If the fire suppression system fails to extinguish the fire, rapid compression of the
chamber with helium may extinguish the fire, in that helium lowers the oxygen
concentration and promotes heat transfer. After the fire is extinguished, chamber
atmosphere contaminant emergency procedures shall be followed.
PTC Emergencies.
PTC emergencies, like DDC emergencies, require specific,
timely, and uniform responses in order to prevent injury or casualty to divers,
watchstanders, and equipment.
Saturation decompression may be initiated by an upward excursion as long as the
excursion remains within the limits permitted by the Unlimited Duration Excur-
sion Tables. The alternative is to begin travel at the appropriate decompression
rate without the upward excursion. Decompression travel rates are found on Table
Upward Excursion Depth.
The minimum depth to which the upward excursion
may be made is found by entering Table 15-8 with the deepest depth attained by
any diver in the preceding 48 hours. The total upward excursion actually chosen is
determined by the Diving Officer and Master Diver, and approved by the
Commanding Officer, taking into consideration environmental factors, the divers
workload, and the divers physical condition.
Travel Rate.
The travel rate for the upward excursion is 2 fsw/min. Beginning
decompression with an upward excursion will save considerable time and may be
used whenever practical.
Post-Excursion Hold.
Due to the increased risk of decompression sickness
following an upward excursion for dives with a storage depth of 200 fsw or less, a
2-hour post-excursion hold should be utilized. The 2-hour hold begins upon arrival
at upward excursion depth.
Rest Stops.
During decompression, traveling stops for a total of 8 hours out of
every 24 hours. The 8 hours should be divided into at least two periods known as
Table 15-9. Saturation Decompression Rates.
Depth Rate
1,600 – 200 fsw 6 feet per hour
200 – 100 fsw 5 feet per hour
100 – 50 fsw 4 feet per hour
50 – 0 fsw 3 feet per hour
15-34 U.S. Navy Diving Manual—Volume 3
“Rest Stops.” At what hours these rest stops occur are determined by the daily
routine and operations schedule. The 2-hour post-excursion hold may be consid-
ered as one of the rest stops.
Saturation Decompression Rates.
Table 15-9 shows saturation decompression
rates. In practice, saturation decompression is executed by decompressing the
DDC in 1-foot or 2-foot increments when indicated in the dive protocol. For
example, using a travel rate of 6 feet per hour will decompress the chamber 1 foot
every 10 minutes. The last decompression stop before surfacing may be taken at 4
fsw to ensure early surfacing does not occur and that gas flow to atmosphere
monitoring instruments remains adequate. This last stop would be 80 minutes,
followed by direct ascent to the surface at 1 fsw/min.
Traveling is conducted for 16 hours in each 24-hour period. A 16-hour daily
travel/rest outline example consistent with a normal day/night cycle is:
This schedule minimizes travel when the divers are normally sleeping. Such a
daily routine is not, however, mandatory. Other 16-hour periods of travel per 24-
hour routines are acceptable, although they shall include at least two stop periods
dispersed throughout the 24-hour period and travel may continue while the divers
sleep. An example of an alternate schedule is:
The timing of the stop is dependent upon operational requirements. The travel rate
between stops should not exceed 1 fsw per minute.
Atmosphere Control at Shallow Depths.
As previously stated, the partial pres-
sure of oxygen in the chamber shall be maintained between 0.44 and 0.48 ata, with
two exceptions. The first is just before making the initial Upward Excursion and
the second during the terminal portion of saturation decompression. Approxi-
mately 1 hour before beginning an Upward Excursion, the chamber ppO
may be
increased up to a maximum of 0.6 ata to ensure that the ppO
after excursion does
not fall excessively. The ppO
should be raised just enough so the post-excursion
does not exceed 0.48 ata. However, when excursions begin from depths of
Daily Routine Schedule
2400–0600 Rest Stop
0600–1400 Travel
1400–1600 Rest Stop
1600–2400 Travel
Alternate Sample Schedule
2300–0500 Travel
0500–0700 Rest Stop
0700–0900 Travel
0900–1500 Rest Stop
1500–2300 Travel
CHAPTER 15 — Saturation Diving 15-35
200 fsw or shallower, a pre-excursion ppO
of 0.6 ata will result in a post-excur-
sion ppO
of less than 0.44 ata. In these cases, the pre-excursion ppO
should not
exceed 0.6 ata, but the post-excursion ppO
should be increased as rapidly as
The second exception is at shallow chamber depth. As chamber depth decreases,
the fractional concentration of oxygen necessary to maintain a given partial pres-
sure increases. If the chamber ppO
were maintained at 0.44–0.48 ata all the way
to the surface, the chamber oxygen percentage would rise to 44–48 percent.
Accordingly, for the terminal portion of saturation decompression, the allowable
oxygen percentage is between 19 and 23 percent. The maximum oxygen
percentage for the terminal portion of the decompression shall not exceed 23
percent, based upon fire-risk considerations.
Saturation Dive Mission Abort.
If it is necessary to terminate a saturation dive
after exceeding the abort limits (see paragraph 15-20.4), standard saturation
decompression procedures shall be followed.
Emergency Cases.
In exceptional cases it could be necessary to execute a
mission abort and not be able to adhere to standard saturation decompression
procedures. The emergency abort procedures should only be conducted for grave,
unforeseen casualties that require deviation from the standard decompression
procedures such as:
An unrepairable failure of key primary and related backup equipment in the
dive system that would prevent following standard decompression procedures.
Unrepairable damage to the diving support vessel or diving support facility.
A life-threatening medical emergency where the risk of not getting the patient
to a more specialized medical care facility outweighs the increased risk of pul-
monary oxygen toxicity and increased risk of decompression sickness
imposed upon the patient by not following standard saturation decompression
An Emergency Abort Procedure was developed and has received limited testing. It
enables the divers to surface earlier than would be allowed normally. However,
the time saved may be insignificant to the total decompression time still required,
especially if the divers have been under pressure for 12 hours or more. In addition,
executing the Emergency Abort Procedure increases the divers risk for decom-
pression sickness and complications from pulmonary oxygen toxicity.
Before executing a mission abort procedure that does not follow standard decom-
pression procedures or the abort procedures contained in paragraph 15-20.4, the
Commanding Officer must carefully weigh the risk of the action, relying on the
advice and recommendations of the Master Diver, Diving Officer, and Saturation
Diving Medical Officer. Specifically, it must be determined if the time saved will
benefit the divers life despite the increased risks, and whether the Emergency
Abort Procedure can be supported logistically.
15-36 U.S. Navy Diving Manual—Volume 3
NOTE USN dive system desi
n incorporates separate primary, secondary, and
as supplies and redundancy of key equipment. It is neither
the intent of this section nor a requirement that saturation dive systems
be confi
ured with additional
as stores specifically dedicated to exe-
cution of an emer
ency abort procedure. Au
as supplies if
required will be
ained by returnin
to port or receivin
additional sup-
plies on site.
Except in situations where the nature or time sensitivity of the emergency does not
allow, technical and medical assistance should be sought from the Navy Experi-
mental Diving Unit prior to deviating from standard saturation decompression
Emergency Abort Procedure.
Emergency Abort Procedures should only be
conducted for grave casualties that are time critical. Decompression times and
chamber oxygen partial pressures for emergency aborts from helium-oxygen satu-
ration are shown in Table 15-10.
Emergency Abort decompression is begun by making the maximum Upward
Excursion allowed by Table 15-8. Rate of travel should not exceed 2 fsw/min. The
upward excursion includes a 2-hour hold at the upward excursion limit. Travel
time is included as part of the 2-hour hold. Following the Upward Excursion, the
chamber oxygen partial pressure is raised to the value shown in Table 15-10.
Decompression is begun in 1-foot increments using the times indicated in Table
15-10. Rate of travel between stops is not to exceed 1 fsw/min. Travel time is
included in the next stop time. The partial pressure of oxygen is controlled at the
value indicated until the chamber oxygen concentration reaches 23 percent. The
oxygen concentration is then controlled between 19 and 23 percent for the
remainder of the decompression. Stop travel at 4 fsw until total decompression
time has elapsed and then travel to the surface at 1 fsw/min.
For example, the maximum depth of the diver in the last 48 hours was 400 fsw,
and the Commanding Officer approves using the Emergency Abort Procedure.
From the Upward Excursion Table, the complex travels to 307 fsw at a rate not to
exceed 2 fsw/min. It takes 46.5 minutes to travel. This time is part of a 2-hour hold
requirement as part of the upward excursion for emergency aborts.
Table 15-10. Emergency Abort Decompression Times and Oxygen Partial Pressures.
Post Excursion Depth
One-Foot Stop Time (min)
1000–200 fsw 200–0 fsw
0–203 0.8 11 18
204–272 0.7 11 19
273–1000 0.6 12 21
CHAPTER 15 — Saturation Diving 15-37
Because the post-excursion depth is between 273–1,000 fsw, the chamber oxygen
partial pressure is raised to 0.6 ata. Once the atmosphere is established and the
remainder of the 2-hour hold completed, begin decompression in 1-foot incre-
ments with stop times of 12 minutes from 307 to 200 fsw. The travel rate between
stops should not exceed 1 fsw/min. Travel time is included in the stop time. It will
take 21.4 hours to arrive at 200 fsw.
At 200 fsw the 1-foot stop time changes to 21 minutes. It will take 70 hours to
reach the surface. The total decompression time is 93.4 hours (3 days, 21 hours, 21
minutes, 36 seconds). By contrast, standard saturation decompression would take
approximately 4 days and 3 hours to complete.
During and following the dive, the divers should be monitored closely for signs of
decompression sickness and for signs of pulmonary oxygen toxicity. The latter
includes burning chest pain and coughing. The divers should be kept under close
observation for at least 24 hours following the dive.
If the emergency ceases to exist during the decompression, hold for a minimum of
2 hours, revert to standard decompression rates, and allow the oxygen partial pres-
sure to fall to normal control values as divers consume the oxygen. Venting to
reduce the oxygen level is not necessary.
Decompression Sickness (DCS).
Decompression sickness may occur during a
saturation dive as a result of an Upward Excursion or as a result of standard satura-
tion decompression. The decompression sickness may manifest itself as
musculoskeletal pain (Type I) or as involvement of the central nervous system and
organs of special sense (Type II). Due to the subtleness of decompression sickness
pain, all divers should be questioned about symptoms when it is determined that
one diver is suffering from decompression sickness. For treatment, refer to Figure
Type I Decompression Sickness.
Type I Decompression Sickness may result
from an Upward Excursion or as the result of standard saturation decompression.
It is usually manifested as the gradual onset of musculoskeletal pain most often
involving the knee. Divers report that it begins as knee stiffness that is relieved by
motion but which increases to pain over a period of several hours. Care must be
taken to distinguish knee pain arising from compression arthralgia or injury
incurred during the dive from pain due to decompression sickness. This can
usually be done by obtaining a clear history of the onset of symptoms and their
progression. Pain or soreness present prior to decompression and unchanged after
ascent is unlikely to be decompression sickness. Type I Decompression Sickness
that occurs during an Upward Excursion or within 60 minutes immediately after
an Upward Excursion shall be treated in the same manner as Type II Decompres-
sion Sickness, as it may herald the onset of more severe symptoms. Type I
Decompression Sickness occurring more than 60 minutes after an Upward Excur-
sion or during saturation decompression should be treated by recompressing in
increments of 5 fsw at 5 fsw/min until distinct improvement of symptoms is indi-
cated. Recompression of more than 30 fsw is usually unnecessary. Once treatment
15-38 U.S. Navy Diving Manual—Volume 3
Figure 15-9.
Saturation Decompression Sickness Treatment Flow Chart.
CHAPTER 15 — Saturation Diving 15-39
depth is reached, the stricken diver is given a treatment gas, by BIBS mask, with
an oxygen partial pressure between 1.5 and 2.8 ata. Interrupt treatment gas
breathing every 25 minutes with 5 minutes of breathing chamber atmosphere.
Divers should remain at treatment depth for at least 2 hours on treatment gas
following resolution of symptoms. Decompression can then be resumed using
standard saturation decompression rates. Further Upward Excursions are not
Type II Decompressions Sickness.
Type II Decompression Sickness in saturation
diving most often occurs as a result of an Upward Excursion. The onset of symp-
toms is usually rapid, occurring during the Upward Excursion or within the first
hour following an excursion ascent. Inner ear decompression sickness manifests
itself as nausea and vomiting, vertigo, loss of equilibrium, ringing in the ears and
hearing loss. Central nervous system (CNS) decompression sickness may present
itself as weakness, muscular paralysis, or loss of mental alertness and memory.
Type II Decompression Sickness resulting from an Upward Excursion is a medical
emergency and shall be treated by immediate recompression at 30 fsw/min to the
depth from which the Upward Excursion originated. When Type II Decompres-
sion Sickness symptoms do not occur in association with an Upward Excursion,
compression at 5 fsw/min to the depth where distinct improvement is noted should
take place. Upon reaching treatment depth, symptoms usually begin to abate
rapidly. If symptoms are not significantly improved within 5 to 10 minutes at the
initial treatment depth, deeper recompression at the recommendation of a Satura-
tion Diving Medical Officer should be started until significant relief is obtained.
After reaching the final treatment depth, treatment gas having an oxygen partial
pressure of 1.5 to 2.8 ata shall be administered to the stricken diver for 25-minute
periods interspersed with 5 minutes of breathing chamber atmosphere. Treatment
gas shall be administered for at least 2 hours and the divers shall remain at the
final treatment depth for at least 12 hours following resolution of symptoms.
Decompression can then be resumed using standard saturation decompression
using rates shown in Table 15-9. Further Upward Excursions are not permitted.
After surfacing from the dive, the divers are still at risk from decompression sick-
ness. Divers shall remain in the immediate vicinity of a chamber for 2 hours and
within 30 minutes travel of a chamber for 48 hours after the dive. Divers shall not
fly for 72 hours after the dive surfaces.
15-40 U.S. Navy Diving Manual—Volume 3