Dive Planning 8

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8.0 GENERAL ...... 8- 1 8.1 DIVE PLANNING...... 8- 1 8.1.1 Selection of Diving Equipment ...... 8- 2 8.2 DIVE TEAM ORGANIZATION ...... 8- 2 8.2.1 Divemaster ...... 8- 2 8.2.2 Diving Medical Officer/ Diving Medical Technician ...... 8- 3 8.2.3 Science Coordinator ...... 8- 3 8.2.4 Divers...... 8- 3 8.2.5 Support Divers and Other Support Personnel ...... 8- 3 8.3 ENVIRONMENTAL CONDITIONS ...... 8- 3 8.3.1 Surface Environmental Conditions ...... 8- 3 8.3.2 Underwater Environmental Conditions ...... 8- 4 8.4 DIVING SIGNALS ...... 8- 8 8.4.1 Hand Signals ...... 8- 8 8.4.2 Surface-to-Diver Recall Signals ...... 8-11 8.4.3 Line Signals ...... 8-11 8.4.4 Surface Signals ...... 8-11 8.5 AIR CONSUMPTION RATES ...... 8-11 8.5.1 Determining Individual Air Utilization Rates ...... 8-14 8.5.2 Scuba Duration ...... 8-14 8.5.3 Scuba Air Requirements ...... 8-16 8.5.4 Surface-Supplied Air Requirements...... 8-17 Dive Planning 8

8.0 GENERAL – Open-circuit scuba Diving with air as the breathing gas is conducted – Rebreathers using a variety of life-support equipment. The most fre- – Surface-supplied quently used mode is open-circuit scuba, where the diver – Hookah carries the compressed air supply. Divers can also use •Equipment and Supplies Selection umbilical-supplied air with a scuba regulator, and either a – Breathing gas, including a backup supply full-face mask or a lightweight diving helmet. This section – Dive platform and support equipment, including deals with planning for air dives, operational methods of diver/crew shelter calculating air supply requirements, personnel require- – Oxygen resuscitator and first aid kit ments, and environmental conditions. – Backboard – Dive flag 8.1 DIVE PLANNING – Diving gear, tools, etc. – Water Careful and thorough planning are the keys to con- ducting an efficient diving operation and are imperative – Communications for diver safety as well. The nature of each dive operation •Schedule of Operational Tasks for All Phases determines the scope of the planning required. The dive – Transit to the site plan should take into account the ability of the least quali- – Assembling dive gear and support equipment fied diver on the team and be flexible enough to allow for – Predive briefing delays and unforeseen problems. It should include at least – Calculating allowable/required bottom time the following: – Recovery – Cleaning, inspection, repair, and storage of gear •Definition of Objectives – Debriefing of divers and support personnel – A clear statement of the purpose and goals of the •Final Preparations and Safety Checks operation – Review of dive plan, its effect, and all safety pre- •Analysis of Pertinent Data cautions – Surface conditions, such as sea state, air tempera- – Outline diving assignments and sequence ture, and wind chill factor – Complete and post on-site emergency checklist – Underwater conditions, including water tempera- – Review diver qualifications and conditions ture, depth, type of bottom, tides and currents, – Secure permission from command or boat captain visibility, extent of pollution, and hazards for dive – Assistance and emergency information, including •Briefing/Debriefing the Diving Team location, status, and contact procedures for the – The objective and scope of the operation nearest recompression chamber, air evacuation – Conditions in the operating area team, U.S. Coast Guard, and nearest hospital – Diving techniques and equipment to be used •Diving Team Selection – Personnel assignments – Divemaster – Specific assignments for each diver – Medical personnel – Anticipated hazards – Tenders/timekeeper – Normal safety precautions – Coxswain/surface-support personnel – Any special considerations •Diving Mode Selection – Group discussion period to answer questions by – Skin (snorkeling) members of the diving team 8-1 8.1.1 Selection of Diving Equipment Umbilical-Supplied Systems The selection of the proper diving equipment depends on environmental conditions, qualifications of Generally Used For: diving personnel, objectives of the operation, and diving •Scientific investigation procedures to be used. Although most diving is per- •Ship repair and inspection formed at depths less than 130 ft. (39.6 m) and often • Salvage uses open-circuit scuba, some missions can be accom- •Long-duration scientific observation and data plished using only skin diving equipment. Other more gathering complex assignments require surface-supplied or closed- •Harsh environments (low visibility, strong currents, circuit systems. Depth and duration of the dive, ques- polluted water) tions about the type of work to be accomplished (heavy Major Advantages: work, light work, silent work), temperature of the •Long duration water, velocity and nature of current, visibility, logis- •Voice communication tics, and the diver’s experience and capabilities all influ- •Protection of diver from environment ence the selection of diving equipment. Detailed Major Disadvantages: descriptions of the various types of diving equipment •Limited mobility are presented in Chapter 5. For planning purposes, the •Significant support requirements following guidelines may be used in selecting the appropriate diving equipment. Closed-Circuit Systems Generally Used For: Breath-Hold Diving Equipment •Observations of long duration Major Advantages: Generally Used For: •Mixed-gas capability •Scientific observation and specimen collection in •No noise or bubbles shallow water in areas where more complex equip- •Conservation of breathing medium ment is a disadvantage or is not available •Long duration •Shallow-water photography Major Disadvantages: •Scouting for diving sites •Complicated maintenance Major Advantages: •Extensive training requirements •Less physical work required to cover large surface •Cost of equipment areas •Simplified logistics 8.2 DIVE TEAM ORGANIZATION •Fewer medical/physiological complications 8.2.1 Divemaster Major Disadvantages: NOAA Divemasters have complete responsibility for the •Extremely limited in depth and duration safe and efficient conduct of all NOAA diving operations. In •Requires diver to develop breath-holding tech- order to be a NOAA Divemaster, individuals must be certi- niques fied NOAA Working Divers, or higher, and have completed •Can only be used in good sea conditions the NOAA Divemaster training program. When no divemaster is present, diving should not be conducted. The divemas- Open-Circuit Scuba ter’s responsibilities include, but are not limited to:

Generally Used For: •Overall responsibility for the diving operation •Scientific observation •Safe execution of all diving •Light underwater work and recovery •Preparation of a basic plan of operation, including •Sample collection evacuation and accident management plans •Shallow-water research •Liaison with other organizations •Ship inspection and light repair •Inspection of equipment Major Advantages: •Proper maintenance, repair, and stowage of equip- •Minimum support requirements ment • Mobility •Selection, evaluation, and briefing of divers and •Accessibility and economy of equipment and other personnel breathing medium •Monitoring progress of the operation, and updating • Portability requirements as necessary • Reliability •Maintaining the diving log Major Disadvantages: •Monitoring of decompression (when required) •Lack of efficient voice communication •Coordination of boat operations when divers are in •Limited depth and duration the water 8-2 NOAA Diving Manual The divemaster is responsible for assigning all divers to The chief scientist is the prime point of contact for all an operation and for ensuring that their qualifications are scientific aspects of the program, including scientific adequate for the requirements of the dive. The divemaster equipment, its use, calibration, and maintenance. must ensure that all divers are briefed thoroughly about the Working with the divemaster, the chief scientist will mission and goals of the operation. Individual responsibili- brief divers on specific scientific tasks to be completed ties are assigned to each diver by the divemaster. Where spe- and supervise the debriefing and sample or data accumu- cial tools or techniques are to be used, the divemaster must lation after a dive. ensure that each diver is familiar with their application. Training and proficiency dives should be made to 8.2.4 Divers ensure safe and efficient operations. During complex opera- Although the divemaster is responsible for the overall tions or those involving a large number of divers, divemas- diving operation, the diver is responsible for being in ters should perform no diving, but should, instead, devote proper physical condition, for checking out personal their efforts entirely to directing the operation. equipment before the dive, and for thoroughly under- The divemaster is in charge when divers are in the standing the purpose and the procedures to be used for the water during diving operations. Before any change is made dive. The diver is also responsible for refusing to dive to the boat’s propulsion system (e.g., change in speed, when conditions are unsafe, when not in good mental or direction, etc.), the boat captain must consult with the physical condition, or when diving would violate dictates divemaster. of their training or applicable standards.

8.2.2 Diving Medical Officer/Diving Medical 8.2.5 Support Divers and Other Support Personnel Technician In most diving operations, the number and types of When it is not practical to have a qualified diving med- support divers depend on the size of the operation and the ical officer on site, a Diving Medical Technician trained in type of diving equipment used. Ideally, those surface-sup- the care of diving casualties shall be assigned. The DMT is port personnel working directly with the diver also should trained to respond to emergency medical situations and to be qualified divers. Using unqualified personnel who do communicate effectively with a physician not at the diving not understand diving techniques and terminology may cause confusion and can be dangerous. Persons not quali- site. There are specialized courses available to train Diving fied as divers can be used when the need arises, but only Medical Technicians in the care of diving casualties. after they have demonstrated that they understand proce- In the event that neither a physician nor a trained tech- dures to the satisfaction of the divemaster. nician is available, the divemaster should have available the names and phone numbers of at least three diving medical specialists who can be reached for advice in an emergency. 8.3 ENVIRONMENTAL CONDITIONS Emergency consultation is available from the service centers Environmental conditions at a dive site should be con- listed below. Referred to as a “Bends Watch,” each of these sidered when planning a diving operation. Environmental services is available to provide advice on the treatment of conditions can be divided into surface conditions and diving casualties: underwater conditions. Surface conditions include weather, sea state, and amount of ship traffic. Underwater condi- •Divers Alert Network, Peter B. Bennett Center, 6 tions include depth, bottom type, currents, water tempera- West Colony Place, Durham, North Carolina 27705, tures, and visibility. Regional and special diving conditions are discussed in Chapter 12. telephone (919) 684-8111 (ask for the Diving Accident Physician) 8.3.1 Surface Environmental Conditions •Navy Experimental Diving Unit, Panama City, When planning a dive, weather conditions are an Florida 32407, telephone (850) 234 - 4351 important factor. Whenever possible, diving operations •Brooks Air Force Base, San Antonio, Texas 78235, should be cancelled or delayed during bad weather. telephone (210) 536-3278 (before 7:00 a.m. and Current and historical weather data should be reviewed to after 4:15 p.m. MST), emergency call (210) 536- determine if conditions are acceptable and are predicted to 3281 (Monday thru Friday between 7:00 a.m. and continue long enough to complete the mission. Continuous 4:15 p.m. MST) marine weather broadcasts are provided by NOAA on the following frequencies depending on the local area: All diving personnel shall have access to the phone numbers of these facilities, available at all times, especially if 162.40 MHz, 162.475 MHz, or 162.55 MHz they will be diving in remote areas. These broadcasts can be heard in most areas of the United 8.2.3 Science Coordinator States and require only the purchase of a VHF radio On missions where diving is performed in support of receiver. Weather radios are designed to receive only scientific programs, a chief scientist may be needed. NOAA radio broadcasts. Regular weather forecasts and

Dive Planning 8-3 SS6 Waves Start to Roll

SS5 Spindrift Forms

SS3 White Caps Form Wave Height ~ Feet (Avg)

FIGURE 8.1 Sea States special marine warnings are available any time of the day or Take the necessary precautions to ensure that they night. Although both receivers pick up weather signals from remain clear of the area. approximately the same distance, the two-way systems have Surface visibility is important. Reduced visibility may the advantage of transmission quality. seriously hinder or force postponement of diving opera- In some cases, surface weather conditions may influ- tions. If operations are to be conducted in a known fog ence the selection of diving equipment. For instance, even bank, the diving schedule should allow for probable delays though water temperature may permit the use of standard caused by low visibility. The safety of the diver and sup- wetsuits, cold air temperature and wind may dictate that a port crew is the prime consideration in determining dry suit (or equivalent) should be worn when diving from whether surface visibility is adequate. For example, in low an open or unheated platform. surface visibility conditions, a surfacing scuba diver might Whenever possible, avoid or limit diving in moderate not be able to find the support craft or might be in danger seas. Sea state limitations depend to a large degree on the of being struck by surface traffic. type and size of the diving platform. Diving operations may be conducted in rougher seas from properly moored 8.3.2 Underwater Environmental Conditions larger platforms such as diving barges, ocean-going ships, Dive depth is a basic consideration in the selection of or fixed structures. When using self-contained equipment, personnel, equipment, and techniques. Depth should be divers should avoid entering the ocean in heavy seas or determined as accurately as possible in the planning phases, surf, as well as high, short-period swell. If bad weather and dive duration, air requirements, and decompression sets in after a diving operation has commenced, all divers schedules should be planned accordingly. should be recalled. Except in an emergency, divers should The type of bottom affects divers ability to see and not attempt scuba or surface-supplied diving in rough seas work. Mud (silt and clay) bottoms generally are the most (see Figure 8.1 and Table 8.1). limiting because the slightest movement will stir sediment Because many diving operations are conducted in into suspension, restricting visibility. The diver must orient harbors, rivers, or major shipping channels, the pres- himself so that any current will carry the suspended sedi- ence of ship traffic often presents serious problems. At ment away from the work area. Also, the diver should times, it may be necessary to close off the area around develop a mental picture of his surroundings so that his safe the dive site or to limit the movement of ships in the ascent to the surface is possible even in conditions of zero vicinity of the dive site. Ship traffic should be consid- visibility. ered during dive planning, and a local “Notice to Sand bottoms usually present little problem because vis- Mariners” should be issued. Anytime diving operations ibility restrictions caused by suspended sediment are less are to be conducted in the vicinity of other ships, other severe than with mud bottoms. In addition, sandy bottoms vessels should be notified by message or signal that div- provide firm footing. ing is taking place. Signal flags, shapes, and lights are Coral reefs are solid but contain many sharp protru- shown in Table 8.2. sions. Divers should wear gloves and coveralls or a wet- If the dive operation is to be conducted in the middle suit for protection if the operation requires contact with of an active fishing ground, divers must assume that peo- the coral. Learn to identify and avoid corals and other ple with various levels of experience and competence marine organisms that might inflict injury. There’s also will be operating small boats in the vicinity and may not the concern of not inflicting unnecessary damage to the be acquainted with the meaning of diving signals. environment during the process of studying it.

8-4 NOAA Diving Manual TABLE 8.1 Sea State Chart

Sea-General Wind Sea

Wave Height Feet

Sea State Description t (Average Period) Significant Range of Periods (Seconds) Average 1/10 Highest Average Minimum Duration (Hours) Minimum Fetch (Nautical Miles) (Beaufort) Wind Force Description Range (Knots) Wind Velocity (Knots) I (Average Wave Length)

Sea like a mirror UCalmLess0 0 0 – – – – – 0 than 1

Ripples with the 1 Light 1–3 2 0.05 0.10 up to 0.5 10 in. 5 18 1 appearance of scales Airs 1.2 sec. min. are formed, but without foam crests.

Small wavelets still, but 2 Light 4–6 5 0.18 0.37 0.4–2.8 1.4 6.7 ft. 8 39 more pronounced; short Breeze min. crests have a glassy appearance, but do not break.

Large wavelets, crests 3 Gentle 7.10 8.5 0.6 1.2 0.8–5.0 2.4 20 9.8 1.7 2 begin to break. Foam of Breeze 10 0.88 1.8 1.0–6.0 2.9 27 10 2.4 glassy appearance. Perhaps scattered white caps.

Small waves, becoming 4 Moderate 11–16 12 1.4 2.8 1.0–7.0 3.4 40 18 3.8 3 larger, fairly frequent white Breeze 13.5 1.8 3.7 1.4–7.6 3.9 52 24 4.8 caps. 14 2.0 4.2 1.5–7.8 4.0 59 28 5.2 16 2.9 5.8 2.0–8.8 4.6 71 40 6.6

Moderate waves, taking a 5 Fresh 17–21 18 3.8 7.8 2.5–10.0 5.1 90 55 8.3 4 more pronounced long Breeze 19 4.3 8.7 2.8–1.0.6 5.4 95 65 9.2 form; many white caps 20 5.0 10 3.0–11.1 5.7 111 75 10 are formed. (Chance of some spray.)

Large waves begin to form, 6 Strong 22–27 22 6.4 13 3.4–12.2 6.3 134 100 12 5 the white foam crests are Breeze 24 7.9 16 3.7–13.5 6.8 160 130 14 more extensive everywhere. 24.5 8.2 17 3.8–13.6 7.0 164 140 15 (Probably some spray.) 26 9.6 20 4.0–14.5 7.4 188 180 17

Sea heaps up and white 7 Moderate 28–33 28 11 23 4.5–15.5 7.9 212 230 20 6 foam from breaking waves Gale 30 14 28 4.7–16.7 8.6 250 280 23 begins to be blown in streaks 30.5 14 29 4.8–17.0 8.7 258 290 24 along the direction of the 32 16 33 5.0–17.5 9.1 285 340 27 wind. (Spindrift begins to be seen.)

Dive Planning 8-5 TABLE 8.1 Sea State Chart (continued)

Sea-General Wind Sea

Wave Height Feet

Moderately high waves of 8 Fresh 34–40 34 19 38 5.5–18.5 9.7 322 420 30 7 greater length; edges of Gale 36 21 44 5.8–19.7 10.3 363 500 34 crests break into spindrift. 37 23 46.7 6–20.5 10.5 376 530 37 The foam is blown in well 38 25 50 6.2–20.8 10.7 392 600 38 marked streaks along the 40 28 58 6.5–21.7 11.4 444 710 42 direction of the wind. Spray affects visibility.

High waves. Dense streaks 9 Strong 41–47 42 31 64 7–23 12.0 492 830 47 8 of foam along the direction Gale 44 36 73 7–24.2 12.5 534 960 52 of the wind. Sea begins to 46 40 81 7–25 13.1 590 1110 57 roll. Visibility affected.

Very high waves with long 10 Whole 48–55 48 44 90 7.5–26 13.8 650 1250 63 overhanging crests. The Gale 50 49 99 7.5–27 14.3 700 1420 69 resulting foam is in great 51.5 52 106 8–28.2 14.7 736 1560 73 patches and is blown in 52 54 110 8–28.5 14.8 750 1610 75 dense white streaks along 54 59 121 8–29.5 15.4 810 1800 81 the direction of the wind. On the whole, the surface of the sea takes a white appearance. The rolling of the sea becomes heavy and shock- like. Visibility is affected.

Exceptionally high waves. 11 Storm 56–63 56 64 130 8.5–31 16.3 910 2100 88 9 (Small and medium-sized 59.5 73 148 10–32 17.0 985 2500 101 ships might be lost to view behind the waves for a long time.) The sea is completely covered with long white patches of foam lying along the direction of the wind. Everywhere the edges of the wave crests are blown into froth. Visibility affected.

Air filled with foam and 12 Hurricane 64–71 >64 >80 >164 10–(35) (18) spray. Sea completely white with driving spray; visibility very seriously affected.

8-6 NOAA Diving Manual TABLE 8.2 Signal Flags, Shapes, and Lights

Signal Use Meaning

White Red

Displayed by civilian divers in the United "Divers are below. Boats should not States. May be used with code flag alpha operate within 100 feet." (flag A), but cannot be used in lieu of flag A. (Varies in accordance with The Coast Guard recommends that the red- individual state laws.) and-white diver's flag be exhibited on a float Red marking the location of the divers.

Sport Diver Flag

Must be displayed by all vessels operating "My maneuverability is restricted either in international waters or on the because I have a diver down; keep well navigable waters of the United States that clear at slow speed." are unable to exhibit three shapes (see last row of this table). Flag A means that the maneuverability of the vessel is restricted. White Blue International Code Flag "A"

Yellow "I" Black Displayed by all vessels in international "I am engaged in submarine survey and foreign waters. work (underwater operations); keep Yellow clear of me and go slow." "R" Red

International Code Flags "I and R"

International Day Shapes and Lights

Shapes/Day Lights/Night Displayed by all vessels in international "This vessel is engaged in underwater and foreign waters engaged in underwater operations and is unable to get out of Black Red operations. the way of approaching vessels." Ball Black White Diamond

Black Red Ball

Dive Planning 8-7 Currents must be considered when planning and exe- of the mid-Atlantic states. Divers may find that plankton cuting a dive, particularly when using scuba. When a boat absorb most of the light at the thermocline and that even is anchored in a current, a buoyed safety line at least 100 ft. though the water below the thermocline is clear, a light is (30.5 m) in length should be trailed from the stern during still necessary to see adequately. Thermoclines in clear diving operations. If, on entering the water, a diver is swept water diffuse light within the area of greatest temperature away from the boat by the current, the diver can use this change, causing a significant decrease in visibility. safety line to keep from being carried down current. Free-swimming descents should be avoided in cur- WARNING rents, unless a means of retrieving the diver is available in DIVERS SHOULD BE EXTREMELY CAUTIOUS case they miss their intended target. Descent from an AROUND UNDERWATER WRECKS OR OTHER anchored or fixed platform into water with currents should STRUCTURES IN LOW VISIBILITY TO AVOID be made via a down line. A trail line also should be used SWIMMING INADVERTENTLY INTO AN AREA WITH unless a pickup boat is operating down current so that OVERHANGS. divers surfacing some distance from the entry point can be retrieved. A knowledge of changing tidal currents may A well-developed sense of touch is extremely impor- allow the diver to drift down current and to return to the tant when working in low or zero underwater visibility. starting point on the return current. The ability to use touch cues when handling tools or instru- Tidal changes often alter the direction of current and ments in a strange work environment is valuable to a diver sometimes carry sediment-laden water and cause low visibil- in the dark. Rehearsing work functions on the surface ity within a matter of minutes. Tidal currents may prevent while blindfolded will increase proficiency at underwater diving at some locations except during slack tides. Because a tasks. slack tide may be followed by strong currents, divers should Underwater, low-light-level, closed-circuit television know the tides in the diving area and their effects. has been used successfully when light levels are reduced, Currents generally decrease in velocity with depth, because a television camera “sees” more in these condi- and, therefore, it may be easier to swim close to the bottom tions than does the human eye. This is mainly true when when there are swift surface currents. Current direction the reduced visibility is caused by the absence of light; in may change with depth, however. When there are bottom cases where the problem is caused by high turbidity, a TV currents, it is recommended, whenever possible, to start the camera does not offer a significant advantage. When the swim into the current rather than with the current; this purpose of the dive is inspection or observation and a facilitates the return to the entry point at the end of the dive closed-circuit television system is used, the diver serves with the current. Divers should stay close to the bottom essentially as a mobile underwater platform. The monitor and use rocks (if present) to pull themselves along. is watched by surface support personnel who, in turn, Water temperature has a significant effect on the type direct diver movements. Underwater television cameras are of equipment selected and, in some cases, determines the available that are either hand held or mounted on the practical duration of the dive. A thermocline is a boundary diver’s helmet. layer between waters of different temperatures. Although Often a diver will be required to dive in water that con- thermoclines do not pose a direct hazard, their presence tains either waterborne or sediment-contained contami- may affect the selection of diving dress, dive duration, or nants. The health hazards associated with polluted-water equipment. Thermoclines occur at various depths, includ- diving and the equipment to be used on such dives are ing levels close to the surface and in deep water. described in Chapter 13. Temperature may vary from layer to layer. As much as a 20°F (11C) variation has been recorded between the mixed 8.4 DIVING SIGNALS layer (epilimnion) above the thermocline and the deeper 8.4.1 Hand Signals waters (hypolimnion) beneath it. Hand signals are used to convey basic information. Underwater visibility depends on time of day, locality, There are various hand signalling systems presently in use. water conditions, season, bottom type, weather, and cur- Divers in different parts of the country and the world use rents. Frequently, divers will be required to dive in water different signals or variations of signals to transmit the same where visibility is minimal; sometimes, zero. Special precau- message. A set of signals used by NOAA is shown in tions are needed. If scuba is used, a buddy line or other refer- Figure 8.2 and Table 8.4. The signals consist of hand, ence system, and float are recommended. A convenient way instead of finger, motions so divers wearing mittens can to attach a buddy line is to use a rubber loop that can be also use them. To the extent possible, the signals were slipped on and off the wrist easily; this is preferable to tying a derived from those having similar meanings on land. Before line that cannot be removed rapidly. The line should not slip the dive, the divemaster should review the signals shown off so easily, however, that it can be lost inadvertently. with all of the divers. This review is particularly important Heavy concentrations of plankton often accumulate at when divers from different geographical areas constitute a the thermocline, especially during the summer and offshore dive team, or when divers from several organizations are

8-8 NOAA Diving Manual Stop Go Down/Going Down Go Up/Going Up Ok! Ok?

Ok! Ok? Something is Wrong

Distress Low on Air (Need Help)

Out of Air LetÕs Buddy Breathe Danger

FIGURE 8.2 Hand Signals

Dive Planning 8-9 Me, or watch me Come here Go that way I am cold

Which direction? Yes No Take it easy, slow down

Ears not clearing Hold hands Get with your buddy Look

You lead, IÕll follow What time? What Depth? I donÕt understand

FIGURE 8.2 Hand Signals (continued)

8-10 NOAA Diving Manual cooperating in a dive. Signal systems other than hand sig- TABLE 8.3 nals have not been standardized. Whistle blasts, light flash- Line Pull Signals for es, cylinder taps, and hand squeezes generally are used for Surface-to-Diver Communication attracting attention and should be reserved for that purpose.

8.4.2 Surface-to-Diver Recall Signals Unexpected situations often arise that require divers to be called from the water. When voice communication is not available, the following methods should be considered:

•Hammer–rapping four times on a steel hull or metal plate •Bell–held under water and struck four times •Hydrophone–underwater speaker or sound beacon •Strobe–used at night; flashed four times

8.4.3 Line Signals When using surface-supplied equipment, use line signals either as a backup to voice communications to the surface or as a primary form of communication. When using scuba, divers may use line signals in conditions of restricted visibility, for diver-to-diver communications or to communicate with the surface. Table 8.3 describes line signals commonly employed.

NOTE Hand or line signals may vary by geographical area or among organizations. Divers should review signals before diving with new buddies or support personnel.

8.4.4 Surface Signals If a diver needs to attract attention after surfacing and is beyond voice range, the following signaling devices/methods may be used:

•Whistle (diver or scuba air powered) • Flare •Flashing strobe • Flags •Hand/arm signals •Throw water into the air

8.5 AIR CONSUMPTION RATES When considering air consumption rates, three terms need definition:

• Respiratory Minute Volume ( RMV ) is the total volume of air moved in and out of the lungs in one minute. • Actual cubic feet (acf ) is the unit of measure that expresses actual gas volume in accordance with the General Gas Law. • Standard cubic feet (scf ) is the unit of measure expressing surface equivalent volume, under stan- *Standard conditions for gases are defined as 32¡F (0C), 1 ata pressure, and dry gas. dard conditions,* for any given actual gas volume.

Dive Planning 8-11 TABLE 8.4 Hand Signals

Signal Meaning Comment

Hand raised, fingers pointed up, palm to STOP Transmitted in the same way as a Traffic PolicemanÕs receiver STOP

Thumb extended downward from clenched GO DOWN or fist GOING DOWN

Thumb extended upward from clenched fist GO UP or GOING UP

Thumb and forefinger making a circle with OK! or OK? Divers wearing mittens may not be able to extend three remaining fingers extended (if possi- three remaining fingers distinctly (see various draw- ble) ings of signal)

Two arms extended overhead with finger- OK! or OK? A diver with only one free arm may make this signal tips touching above head to make a large by extending that arm overhead with fingertips touch- ÒOÓ shape ing top of head to make the ÒOÓ shape. Signal is for long-range use

Hand flat, fingers together, palm down, SOMETHING This is the opposite of OK! The signal does not indi- thumb sticking out, then hand rocking back IS cate an emergency and forth on axis of forearm WRONG

Hand waving over head (may also thrash Indicated immediate aid required hand on water) DISTRESS

Fist pounding on chest Indicates air supply is reduced to the quantity agreed LOW ON AIR upon in predive planning or air pressure is low and has activated reserve valve

Hand slashing or chopping throat OUT OF AIR Indicates that signaler cannot breathe

Fingers pointing to mouth LETÕS BUDDY The regulator may be either in or out of the mouth BREATHE

Clenched fist, arms extended and forming DANGER a ÒXÓ in front of chest

In computing air consumption rate, the basic deter- Cd = RMV (Pa) minant is the respiratory minute volume, which is direct- where ly related to exertion level and which, because of Cd = consumption rate at depth in scfm individual variation in physiological response, differs RMV = respiratory minute volume in acfm among divers (Cardone 1982). See Table 8.5. Pa = absolute pressure (ata) at dive depth Physiological research has yielded useful estimates of respiratory minute volumes for typical underwater situa- Problem: tions likely to be encountered by most divers (U.S. Navy Compute the air consumption rate for a 50 ft. (15.2 1985). Table 8.6 shows these estimates. These estimates m) dive requiring moderate work, maximum walking of respiratory minute volumes apply to any depth and speed, hard bottom. are expressed in terms of actual cubic feet, or liters, per minute (acfm or alpm, respectively). Solution: The consumption rate at depth can be estimated by Cd = RMV (Pa) determining the appropriate respiratory minute volume for the anticipated exertion level and the absolute pressure of RMV = 1.1 acfm (from Table 8.5) the anticipated dive depth. This estimate, expressed in stan- Pa 50/33 + 1 = 2.51 ata dard cubic feet per minute (scfm), is given by the equation: Cd = (l.l acfm)(2.51 ata) = 2.76 scfm

8-12 NOAA Diving Manual TABLE 8.5 Respiratory Minute Volume (RMV) at Different Work Rates

Activity Respiratory Minute Volume Actual liters / min (STP) Actual cubic ft / min (STP)

LIGHT SLOW WALKING ON HARD BOTTOM UNDER WATER 12 0.42 WORK SWIMMING, 0.5 KNOT (SLOW) 16 0.60

MODERATE SLOW WALKING ON MUD BOTTOM UNDER WATER 20 0.71 WORK SWIMMING, 0.85 knot (av. speed) 26 0.92 MAX. WALKING SPEED, HARD BOTTOM U/W 30 1.1

HEAVY SWIMMING 1.0 KNOT 35 1.2 WORK MAX. WALKING SPEED, MUD BOTTOM U/W 35 1.2

SEVERE SWIMMING, 1.2 KNOTS 53 1.9 WORK

TABLE 8.6 Air Consumption Table at Depth

DEPTH (FEET) 10 15 20 25 30 40 50 60 70 80 90 100 120 140 160 Surface 15 19 21 24 27 28 33 37 42 46 51 55 60 69 78 87 16 20 23 25 28 30 35 40 44 49 54 59 64 73 83 92 17 22 24 27 30 32 37 42 47 52 57 62 68 78 88 98 18 23 26 28 32 34 39 45 50 55 61 66 72 82 93 104 19 24 27 30 34 36 41 47 53 58 64 70 76 87 98 110 20 26 29 32 36 38 44 50 56 62 68 74 80 92 104 116 21 27 30 33 37 39 46 52 58 65 71 77 84 96 109 121 22 28 31 35 39 41 48 55 61 68 74 81 88 101 114 127 23 29 33 36 41 43 50 57 64 71 78 85 92 105 119 133 24 31 34 38 43 45 52 60 67 74 81 88 96 110 124 139 25 32 36 40 45 47 55 62 70 77 85 92 100 115 130 145 26 33 37 41 46 49 57 65 72 80 88 96 104 119 135 150 27 35 39 43 48 51 59 67 75 83 91 99 108 124 140 156 28 36 40 44 50 53 61 70 78 86 95 103 112 128 145 162 29 37 42 46 52 55 63 72 81 89 98 107 116 133 150 168 30 39 43 48 54 57 66 75 84 93 102 111 120 138 156 174 31 40 45 49 55 58 68 77 86 96 105 114 124 142 161 179 32 41 46 51 57 60 70 80 89 99 108 118 128 147 166 185 33 42 47 52 59 62 72 82 92 102 112 122 132 151 171 191 34 44 49 54 61 64 74 85 95 105 115 125 136 156 176 197 35 45 50 56 63 66 77 87 98 108 119 129 140 161 182 203 36 46 52 57 64 68 79 90 100 111 122 133 144 165 187 208 SURFACE AIR CONSUMPTION RATE (PSI PER MINUTE) 37 48 53 59 66 70 81 92 103 114 125 136 148 170 192 214 38 49 55 60 68 72 83 95 106 117 129 140 152 174 197 220 39 50 56 62 70 74 85 97 109 120 132 144 156 179 202 226 40 52 58 64 72 76 88 100 112 124 136 148 160 184 208 232

Dive Planning 8-13 8.5.1 Determining Individual Air Utilization Rates the diver to use Table 8.6 to find the rate at any depth. An alternative approach that can be used expresses The same information can be determined by multiplying air utilization rates in terms of pressure drop in pounds the SAC figure times the depth of the planned dive in per square inch (psi) rather than respiratory minute vol- atmospheres absolute. ume. Keep in mind that usable cylinder pressure is It is important to understand that individuals vary defined as the beginning cylinder pressure minus recom- somewhat from day to day in their air consumption rates, mended air reserve (see Table 8.6). This technique allows and these calculations should thus be considered esti- divers to determine their Surface Air Consumption mates only (Cardone 1982). (SAC) rate which can be used to calculate estimated air consumption rate at any depth. To determine the rate, Problem: read the submersible pressure gauges at the beginning Convert SAC to cubic feet per minute (CFM) by mul- and end of a dive to a constant depth. These readings tiplying the diver’s SAC times the cylinder constant (k) give the information needed to use the simple four-step using formula: procedure shown below: RMV = SAC × k

1. Subtract ending psi (as read from the submersible Solution: pressure gauge) from the beginning psi to deter- The diver in this example had a SAC of 15.71 psi/min 3 mine the amount of air used during the timed dive using a scuba cylinder with a k factor of 0.0267 ft /psi. (∆ psi). RMV= SAC × k 3 2. Using the following formula, determine the diver’s RMV= 15.71 psi/min × 0.0267 ft /psi 3 surface air consumption (SAC) rate: RMV= 0.42 ft /min

∆psi/time (min) 8.5.2 Scuba Duration psi per minute on the surface (SAC)= (depth in ft + 33)/33 Knowing the probable duration of the scuba air supply is vital to proper dive planning. With scuba, the dura- 3. Find the psi per minute on the surface on the left tion of the available air supply is directly dependent on side of the Air Consumption Table (Table 8.6) that the consumption rate. Scuba air supply duration can be is closest to the estimated psi per minute. Read estimated using the equation: across to the desired depth, which will give the esti- Va mated air consumption rate at depth. Da = Cd 4. To estimate how many minutes a cylinder of air where will last at that depth, divide the number of usable Da = duration in minutes psi in the cylinder (as shown on the submersible Va = available volume in scf pressure gauge minus a reserve amount) by the psi Cd = consumption at depth in scfm per minute used at that depth. The available volume depends on the type (rated vol- Problem: ume and rated pressure) and number of cylinders used, A diver swims a distance at 30 ft. (9.1 m) in ten min- the gauge pressure measured, and the recommended minutes; the submersible pressure gauge reads 2,350 psi at the imum cylinder pressure. Consumption rate depends on start and 2,050 at the end of the timed dive, showing that a the depth and the exertion level of the dive. total of 300 psi was consumed. What is the diver’s SAC? The “standard 80 cubic foot” aluminum cylinder has an internal volume of 0.399 cubic feet (11.3 liters) at one The basic equation is: atmosphere. At its rated pressure of 3,000 psig, the cylinder contains a deliverable volume of 81.85 cubic feet ∆psi/time (min) SAC = (2,317.7 liters). (depth in ft + 33)/33 For a given scuba cylinder, the ratio of rated volume to rated pressure is a constant (k = Vr/Pr), mean- Solution: ing that a constant volume of air is delivered for each 300 (psi) ÷ 10 (mins) 30 30 unit of cylinder pressure drop. Mathematically, this = = = 15.7 psi/min results in a linear relationship between gauge pressure (30 (depth) + 33)/33 (63/33) 1.9 and deliverable volume. Figure 8.3 shows this relationship for a 71.2 ft3 (2,016 liters) steel cylinder and an 80 The diver would consume 15.7 psi per minute at the sur- ft3 (2,266 liters) aluminum cylinder. Deliverable vol- face. Knowing the consumption rate at the surface allows umes at any gauge pressure for these two cylinder types

8-14 NOAA Diving Manual can be read directly from Figure 8.3, or they can be For planning purposes, estimates of cylinder duration individually computed using the equation: are based on available air volumes rather than deliverable air volumes. Vd = Pg x k where Problem: Vd = deliverable volume in scf Estimate the duration of a set of twin 80 ft3 (2,318 liters) Pg = gauge pressure in psig aluminum cylinders charged to 2,400 psig for a 70 ft. (21.3 k = cylinder constant m) dive for a diver with a RMV of 0.6 acfm.

This equation can be used for any type of cylinder; Solution: see Table 8.7 for the appropriate cylinder constant. The basic equation for duration is: For planning purposes, the available volume of air is Va Da = the difference between the deliverable volume at a given Cd cylinder pressure and the recommended minimum cylin- where der pressure. The recommended minimum cylinder pres- Da = duration in minutes sures for the two most commonly used scuba cylinder Va = available volume in scf types are shown in Table 8.8. The available volume of air Cd = consumption rate at depth in scfm in the diver’s supply can be determined by the equation: Step 1: Va = N(Pg - Pm)k Determine Va using: where Va = N(Pg - Pm)k Va = available volume in scf Va = 2(2,400 psig - 600 psig) (0.0266 scf/psig) N = number of cylinders = 2(1,800 psig) (0.0266 scf/psig) Pg = gauge pressure in psig = 95.76 scf Pm = recommended minimum pressure in psig k = cylinder constant Step 2: Determine Cd using:

Cd = RMV (Pa) where RMV = respiratory minute volume in acfm Pa = absolute pressure at dive depth

Cd = 0.6 acfm 70 + l ( 33 ) =1.87 acfm

TABLE 8.7 Cylinder Constants

FIGURE 8.3 Deliverable Volumes at Various Gauge Pressures

Dive Planning 8-15 TABLE 8.8 Scuba Cylinder Pressure Data

Steel 72 2475 2250 500 430 Aluminum 80 3000 3000 500 600

TABLE 8.9 Estimated Duration of 80 Ft3 Aluminum Cylinder

ata * * * * *

0 1.0 256.4 91.6 58.3 42.7 29.1 33 2.0 128.2 45.8 29.2 21.4 14.6 66 3.0 85.5 30.5 19.4 14.2 9.7 99 4.0 64.1 22.9 14.6 10.7 7.3 132 5.0 51.3 18.3 11.7 8.5 5.8 165 6.0 42.7 15.3 9.7 7.1 4.8

Step 3: where Solve the basic equation for Da: TAR = total air requirement in scf tdt = total dive time in minutes Va Da = (bottom time plus ascent time at 30 ft/min) Cd Cd = consumption rate at depth in scfm 95.76 scf = Problem 1: 1.87 scfm Estimate the total air requirements for a 30-minute = 51.2 minutes dive to 60 ft. (18.3 m) for a diver with a RMV of .92 acfm. Table 8.9 shows estimates of the duration of a single aluminum 80 ft3 (2,318 l) cylinder at five exertion levels for vari- Solution: ous depths. These estimated durations are computed on Step 1: the basis of an available air volume of 64.1 ft3 (Va = 3,000 Determine tdt. Total dive time is defined as the sum psig - 600 psig) (0.0267 ft3/psig). of the bottom time and normal ascent time at 30 ft/min (9.1 m/min): 8.5.3 Scuba Air Requirements Total air requirements should be estimated when tdt = 30 + 2 = 32 mins planning scuba operations. Factors that influence the total air requirement are depth of the dive, anticipated Step 2: bottom time, normal ascent time at 30 ft/min (9.1 Determine Cd using the equation: m/min), any required stage decompression time, and consumption rate at depth. For dives in which direct Cd = RMV (Pa) ascent to the surface at 30 ft/min (9.1 m/min) is allow- RMV = 0.92 acfm 60 able, the total air requirement can be estimated using the Pa = + 1 = 2.81 ata equation: 33 Cd = (0.92 acfm) (2.81 ata) TAR = tdt (Cd) = 2.59 scfm

8-16 NOAA Diving Manual Step 3: Computation of these estimates during predive plan- Determine TAR using the equation: ning is useful to decide whether changes in assigned tasks, TAR = tdt (Cd) task planning, etc. are necessary to ensure that the dive = (32 mins) (2.59 acfm) can be conducted with the available air supply. However, = 82.88 scf positioning an auxiliary cylinder at the decompression stop is considered a safer practice than relying on calcula- For dives in which stage decompression will be neces- tions of the available air supply. sary, the total air requirement can be estimated using the equation: 8.5.4 Surface-Supplied Air Requirements Estimations of air supply requirements and duration of TAR = Cd (BT + AT) + Cd1T1 + Cd2T2 + Cd3T3 (etc.) air supplies for surface-supplied divers are the same as those of scuba divers except when free-flow or free-flow/demand where Cd1T1, Cd2T2, are the air consumption rates and breathing systems are used; in these cases, the flow, in actu- times at the respective decompression stops. al cubic feet per minute is used (in all calculations) instead of RMV (see Table 8.10). Also, the minimum bank pressure Problem 2: must be calculated to be equal to 220 psig plus the absolute Estimate the total air requirement for an 80-minute dive pressure of the dive (expressed in psia). to 60 ft. (18.3 m) for a diver with a RMV of 0.6 acfm. Problem: Solution: Estimate the air requirements for a 90 ft. (27.4 m) Step 1: dive for 70 minutes with a demand/free-flow helmet. This Determine Cd and Cd1 using the equation: dive requires decompression stops of seven minutes at 20 ft. (6.1 m) and 30 minutes at 10 ft. (3 m). Cd = RMV (Pa) = (0.6 acfm) (2.8 ata) Solution: = 1.68 scfm TAR = Cd (BT + AT) + Cd1T1 + Cd2T2 Step 2: where Determine the total time for the dive, ascent, and TAR = Total Air Requirement decompression stops. For the dive and ascent to the sur- Cd = Consumption rate at depth (scfm) face, add the bottom time (BT) and the ascent time BT = Bottom time (mins) (AT) (to the nearest whole minute) at 30 ft/min (9.1 AT = Ascent time m/min). Pa = Pressure in ata

BT + AT = 80 + 2 = 82 mins Step 1: Determine Cd, Cd1, Cd2: This dive requires a 10-ft. decompression stop. At an ascent rate of 30 ft/min, it will take two minutes to Cd = flow x Pa ascend from 60 ft. (18.3 m) to the surface. = (1.5 acfm)(3.73 ata) = 5.6 scfm The time required for decompression at 10 ft. (3 m) Cd1 = (1.5 acfm)(1.61 ata) = 2.4 scfm is 7 minutes, according to the USN Standard Air Cd2 = (1.5 acfm)(l.30 ata) = 2.0 scfm Decompression Table for a dive to 60 ft. for 80 minutes. Step 2: TAR = Cd (BT + AT) + Cd T 10 1 1 Cd1 = 0.6 () + 1 = 0.78 scfm = 5.6 scf (70 + 3 mins) 33 + 2.4 scf (7 mins) + 2.0 scf (30 mins) = 409 scf + 17 scf + 60 scf (Assume same RMV on decompression stop.) = 486 scf

Cylinder constants for large high-pressure air/gas stor- Step 3: age systems are determined in the same fashion as those Determine TAR using the equation for this case: for scuba cylinders, i.e., rated volume/rated pressure = k. The procedure for determining available volume of TAR = Cd (BT + AT) + Cd1T1 air is also the same as for scuba. For example, = (1.68 scfm) (62 mins) + (0.78 scfm) (7 mins) = 104.2 + 5.5 = 109.7 scf Va = N(Pg - Pm) k

Dive Planning 8-17 where TABLE 8.10 Va = available volume (scf) Flow-Rate Requirements for N = number of cylinders Surface-Supplied Equipment Pg = gauge pressure (psig) Pm = minimum reserve pressure (psig) Equipment Type Flow Rate k = cylinder constant

NOTE If cylinder banks are used as a back-up to a com- Demand/freeflow 1.5 acfm pressor supply, the bank must be manifolded with Free flow 6.0 acfm the primary source so that an immediate switch from primary to secondary air is possible (see Figure 6.10). NOTE: Significant variations in these values can Problem: occur, depending on the flow-valve set by the diver. Determine the number of high-pressure air cylinders Therefore, these values are minimum estimates. required to supply the air for the above dive (486 scf) if the rated volume equals 240 scf, rated pressure equals 2,400 psi, and beginning pressure equals 2,000 psi, using a minimum reserve pressure of 220 psi.

Solution: Step 2: How many cylinders would be required in the bank to sup- Step 1: ply the required amount of gas? How much air could be delivered from each cylinder? vol. required 486 scf Va = N(Pg - Pm)k N = = = 2.8 or 3 cylinders vol/cyl 172.5 scf/cyl 240 scf k = = 0.1 scf/psi 2,400 psi NOTE Calculations for gas supply requirements or scuba Pm = 220 psi + 90 + 33 × 14.7 = 275 psi ()33 duration are for planning purposes only. The diver and tender must continuously monitor the gas Va = 1(2,000 - 275) × 0.1 supply throughout the dive. Va = 172.5 scf/cylinder

8-18 NOAA Diving Manual The NOAA Diving Manual was prepared jointly by the National Oceanic and Atmospheric Administration (NOAA), U.S. Department of Commerce and Best Publishing Company. This CD-ROM product is produced and distributed by the National Technical Information Service (NTIS), U.S. Department of Commerce. Visit our Web site at www.ntis.gov.