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Section Five: The Recreational Dive Planner 5

Section Five

The Recreational Dive PlannerA safe dive plan must take into consideration the avoidance of decompression sickness.Therefore, being able to properly use dive tables is one of the most important skills a divermust possess. As a PADI diver you should know how to use the Recreational Dive Plannerto plan repetitive dives, and how to apply certain table rules. Also, because of its multilevelcapability and other advantages, you should be familiar with how to use The Wheel.

However, just knowing how to use the Recreational Dive Planner isnt enough. You shouldalso understand its theoretical basis. What, for example, are the similarities and differencesbetween the Recreational Dive Planner and other dive tables? What advantage does theRecreational Dive Planner provide over other tables? These are only a few of the issues youneed to know if you are to have a full appreciation and understanding of the subject.

In this section we will review how to use all versions of the Recreational Dive Planner; andyou will have an opportunity to apply rules relating to: emergency decompression; flying anddriving to altitude after diving; omitted decompression; and special procedures when planninmultiple repetitive dives. We will also explore important theoretical issues to ensure that youunderstand not only how the Recreational Dive Planner works, but why.

Objective 5.1

Explain why the Recreational Dive Planner surface interval credit table times aresignificantly shorter than that of the U.S. Navy tables, and why such a difference is possible.

Resources:

Encyclopedia, Chapter Five, under the heading Decompression Models

PADI Divemaster Manual, Chapter Five, under the heading Decompression Theoryand the RDP

Exercises:

1. A 60-minute tissue compartment requires _____________ to fill or empty completely, while

a 120-minute compartment requires _____________.a. 1 hour/2 hours

b. 2 hours/4 hours

c. 6 hours/12 hours

d. 12 hours/24 hours

RESET

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5-2 Diving Knowledge Workbook

2. The U.S. Navy selected the 120-minute tissue compartment to control their SurfaceInterval Credit Table because:

a. they didnt know other compartments could be used.

b. they were designing tables that enabled decompression diving.

c. as most of their diving is surface air supplied, a different decompression modelhad to be used.

d. this was the easiest way to account for individual differences in physiology.

3. The Recreational Dive Planner uses a 60-minute tissue compartment to control itsSurface Interval Credit Table because:

a. there are no safety factors built into its design.

b. the decompression stops are shorter than the Navy tables.

c. it is a better way to account for individual differences in physiology.

d. if divers dont exceed the NDLs the slow 120-minute compartment can bevirtually ignored.

Objective 5.2

Explain what is meant by a multitissue decompression model, and state the numberof tissue compartments used in the creation of the Recreational Dive Planner versusU.S. Navy models.

Resources:

Encyclopedia, Chapter Five, under the heading Decompression Models

PADI Divemaster Manual, Chapter Five, under the heading Decompression Theory

and the RDP

Exercises:

1. The tissue compartments considered within a decompression model are related directly tospecific tissues of the body.

True False2. If the human body is made up primarily of water, why cant decompression theory be

simplified by using a single-tissue model?

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3. In constructing the U.S. Navy Tables _____________ tissue compartments were used todetermine the NDLs. In determining the NDLs for the Recreational Dive Planner _____________ tissue compartments were used.

a. 6/14

b. 6/6

c. 12/12

d. 6/34

4. While several tissue compartments were used to determine the NDLs for both theRecreational Dive Planner and USN tables, only one tissue compartment was used tocontrol the gas wash-out during the surface interval.

True False

Objective 5.3

When diving above sea level, explain why it is critical to know the altitude at which

the dive is to take place.

Resources:

PADIs Adventures in Diving Manual, Section One under the heading Altitude Diving

Exercises:

1. The decompression-related problems encountered when diving at altitude occur becausethe diver begins his dive:

a. at an atmospheric pressure less than that at sea level.

b. at an atmospheric pressure more than that at sea level.

c. with a reduced percentage of nitrogen than that at sea level.

d. with a reduced percentage of oxygen than that at sea level.

2. Because it was designed to allow multilevel diving, there is no need to convert actualdepths into equivalent sea-level depths in order to use the Recreational Dive Planner at300 metres/1000 feet (or higher) above sea level.

True False

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Objective 5.4

Explain why pressure groups from one model/table cannot necessarily be transferredto another model/table.

Resources:

Encyclopedia, Chapter Five, under the heading Decompression Models PADI Divemaster Manual, Chapter Five, under the heading Decompression Theory

and the RDP

Exercises:

1. Because they are based on the same theoretical model, pressure groups may betransferred between the Table and The Wheel version of the Recreational Dive Planner.

True False

2. Upon exiting the water a diver using the Recreational Dive Planner determines he is inpressure group J. Another diver who is using the U.S. Navy tables also determines thathe is in group J. Is it likely that the two divers have approximately the same dive profile?Explain your response.

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Objective 5.5

Using the RDP Table or eRDP and The Wheel, demonstrate how to find a no-decompression limit (NDL), and state the procedures for Emergency Decompressionand Omitted Decompression.

Resources:

For the RDP Table:

PADI Recreational Dive Planner, Instructions for Use

For the eRDP: PADI Electronic Recreational Dive Planner, Instructions for Use

For The Wheel: The Wheel Instructions for Use and Study Guide, Section Two

Exercises:

1. A diver plans a dive to 30 metres/100 feet for 20 minutes. Losing track of time, he noticethat his bottom time is actually 24 minutes. Which of the following procedures should heinstitute in this situation?

a. Immediately ascend to 5 metres/15 feet and make a stop for 15 minutes; avoiddiving for 24 hours.

b. Immediately ascend to 5 metres/15 feet and make a stop for 8 minutes; avoiddiving for 6 hours.

c. Immediately ascend to 5 metres/15 feet and make a stop for 3 minutes.

d. Immediately surface, rest, be monitored for signs of decompression sickness,

breathe 100% oxygen, and do not dive for at least 24 hours.

2. A diver plans a dive to 35 metres for 13 minutes/110 feet for 15 minutes. Upon surfacinghe discovers that he misread his timing device. He was actually at depth for 21 minutes.Which of the following procedures should he institute in this situation?

a. Reenter the water and decompress at 5 metres/15 feet for 15 minutes; avoiddiving for 24 hours.

b. Reenter the water and decompress at 5 metres/15 feet for 8 minutes; avoid divingfor 6 hours.

c. Remain on the surface, rest, be monitored for signs of decompression sickness,

breathe 100% oxygen, and do not dive for at least 24 hours.d. Immediately seek medical attention and recompression treatment.

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3. Using the Table or eRDP, what is the no-decompression limit for a dive to 27 metres/52 feet? _____________ minutes.

4. Using The Wheel, what is the no-decompression limit for a dive to 27 metres/52 feet? _____________ minutes.

Objective 5.6

Using the RDP Table or eRDP and The Wheel, calculate dive profiles for three or morerepetitive dives demonstrating the correct guidelines and procedures for: determiningminimum surface intervals; taking safety stops; and applying the special multiple dive rule.

Resources:

For the Table: PADI Recreational Dive Planner, Instruction for Use

For the eRDP: PADI Electronic Recreational Dive Planner, Instructions for Use

For The Wheel: The Wheel Instructions for Use and Study Guide, Sections Six and Seven

Exercises:

Note: You are to use the Recreational Dive Planner Table or eRDP in completing thefollowing questions. The dive profile illustrations provided will help you keep trackof your calculations. It is recommended that you fill in all appropriate depths, bottomtimes, pressure groups and required safety stops.

1. A diver exits the water at 10:45 a.m. after a dive to 24 metres/78 feet for 21 minutes. At11:15 a.m. he reenters the water for a 36 minute dive to 18 metres/60 feet. If he wishesto make a third dive after only a 2 minute surface interval, what is the maximum depth towhich he may dive and remain for at least 20 minutes?

a. 12 metres/40 feet

b. 15 metres/50 feet

c. 18 metres/60 feet

d. The third dive cannot be made with such a short surface interval.

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2. A diver is planning a dive to 20 metres for 38 minutes/70 feet for 35 minutes. Whatis the minimum amount of time the diver would have to spend at the surface if he wishedto repeat the exact same profile? _____________ minutes

3. A diver is planning a series of 3 dives. Assume he will use minimum surface intervals, followall Recreational Dive Planner rules and dive the following exact profiles. Dive 1 - 24metres for 26 minutes/80 feet for 28 minutes; Dive 2 - 12 metres for 85 minutes/40 feetfor 80 minutes; Dive 3 - 11 metres for 61 minutes/35 feet for 60 minutes. In minutes,

approximately how long will the entire dive profile take to completefrom start to finish?Metric responses: Imperial responses:

a. 201 minutes a. 188 minutes

b. 207 minutes b. 194 minutes

c. 356 minutes c. 356 minutes

d. 362 minutes d. 362 minutes

Note: You are to use the Recreational Dive Planner Wheel in completing the followingquestions. The dive profile illustrations provided will help you keep track of yourcalculations. It is recommended that you fill in all appropriate depths, bottom times,pressure groups and required safety stops.

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4. A diver exits the water at 1:30 p.m. after a dive to 19 metres/63 feet for 34 minutes.He reenters the water at 2:20 p.m. for a dive to 17 metres/55 feet for 24 minutes. Howsoon could the diver reenter the water for a dive to 15 metres/50 feet for 40 minutes?_____________ minutes.

5. A diver exits the water at 10:40 a.m. after a dive to 28 metres/95 feet for 20 minutes.He reenters the water at 12:20 p.m. for a dive to 19 metres/65 feet for 27 minutes. Howsoon could the diver reenter the water for a dive to 17 metres/55 feet for 30 minutes?_____________ minutes.

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Objective 5.7

State the recommendations for flying after diving and demonstrate its use.

Resources:

PADI Open Water Diver Manual, Chapter Five, under the heading, Altitude

Diving, Flying After Diving, and Cold/Strenuous Dives Encyclopedia, Chapter Five, under the heading Flying After Diving

Exercises:

1. A diver exits the water at 10:00 a.m. after a dive to 18 metres/60 feet for 50 minutes.He has made no previous dives. What is the soonest this diver should board a commerciaairliner for his flight home?

a. 2:00 p.m.

b. 10:00 p.m.

c. When he enters pressure group D

d. 10:00 a.m. the next day

2. A diver has been on a diving vacation for a week, during which he made in excess oftwenty dives. He exits the water at 12:00 noon. What is the soonest this diver shouldboard a commercial airliner for his flight home?

a. 2:00 p.m.

b. After 6:00 a.m. the next day

c. When he enters pressure group D

d. 12:00 noon the next day

3. Upon surfacing a diver realizes he has dived the following profile: 29 metres/95 feetfor 23 minutes. What is the soonest this diver should board a commercial airliner for hisflight home?

a. 12 hours after exiting the water

b. more than 18 hours after exiting the water

c. 24 hours after exiting the water

d. Only on the advice of a physician

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Objective 5.8

Using The Wheel, demonstrate how to calculate a multilevel dive.

Resources:

The Wheel Instructions for Use and Study Guide, Section Seven

Exercises:

1. During a multilevel dive, a diver spends 10 minutes at a depth of 34 metres/120 feet.If he then wishes to ascend to 26 metres/85 feet, what would be his remainingno-decompression time during the shallow portion of the dive?

a. 19 minutes

b. 21 minutes

c. 28 minutes

d. The dive cannot be made

as planned as it is beyondthe parameters allowed fora multilevel exposure.

2. A diver is planning a multileveldive. He wishes to stay at34 metres/120 feet for10 minutes, then ascend to24 metres/80 feet for 10 minutes.What will his pressure group beupon exiting the water.

a. Group P

b. Group O

c. Group I

d. The dive cannot be madeas planned.

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Section Five: The Recreational Dive Planner 5-

3. A diver is planning a multilevel dive. He wishes to stay at 34 metres/120 feet for 5minutes, then ascend to 24 metres/80 feet for 22 minutes. What will his pressure groupbe upon exiting the water.

a. Group R

b. Group S

c. Group K

d. The dive cannot be madeas planned as it is outsidethe allowable parametersfor a multilevel exposure.

4. During his safety stop, a diverdetermines he has dived thefollowing profile: 28 metres/90 feet for 15 minutes, ascendingto 18 metres/60 feet for anadditional 23 minutes. What

action should he take as a result?a. Plan any repetitive dive

assuming his endingpressure group is T.

b. Remain at the safetystop for 8 minutes, uponsurfacing; do not dive for6 hours.

c. Remain at the safety stop for 15 minutes, upon surfacing; do not dive for 24 hours

d. Immediately surface, rest, monitor himself for signs of decompression sickness,

breath 100% oxygen and not dive for at least 6 hours.

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Section Five: Answer Key 5-

Correct:ConfidentGuess

Incorrect:Simple MistakeLack of Knowledge



Section Five

Answer KeyObjective 5.1

Explain why the Recreational Dive Planner surface interval credit table times aresignificantly shorter than that of the U.S. Navy tables, and why such a differenceis possible.

1. (c) A 60-minute tissue compartment requires 6 hoursto fill orempty completely, while a 120-minute compartment requires12 hours. The term half-time is simply a way of representingwhat is known as an exponential relationship. In our

discussion of decompression theory its used to describe howquickly a tissue compartment will fill or empty. For example,a tissue compartment described as having a 5-minute half-time will fill (or empty) half of the total amount of nitrogen itcan hold in five minutes. In five more minutes it will be 75%full; in five more minutes 87.5%; in five more 93.6%; in fivemore 96.9% and finally in six half-times (30 minutes total)the compartment is considered full (or empty) at 98.4% of itscapacity (mathematically it never reaches 100%). Therefore, a60-minute tissue will completely fill or empty in 6 hours (60 x 6= 360 mins. or 6 hours). A 120-minute tissue compartment will

fill or empty in 12 hours (120 x 6 = 720 mins. or 12 hours).2. (b) The U.S. Navy selected the 120-minute tissue compartment

to control their Surface Interval Credit Table because: theywere designing tables that enabled decompressiondiving. The primary function of the U.S. Navy tables wasto enable safer decompression diving. They also realizedwith the advent of scuba that provisions were necessary forrepetitive diving. This required consideration of how quicklythe diver lost residual nitrogen. To accommodate this the Navydeveloped a Surface Interval Credit Table. To avoid havingto develop several such tables to be used according to which

tissue compartment controlled the previous dive, they chosean easier approach develop only one table based on asingle compartment. Determining which compartment to usewas simple. As their tables would provide for decompressiondiving even repetitive decompression dives they had to

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use the slowest tissue compartment in their model; one whichwould come into play only during decompression dives. Thatcompartment was the 120-minute compartment, which requires12 hours to fully in or out gas. This explains why it takes up to12 hours to fully out-gas when using the U.S. Navy tables.

3. (d) The Recreational Dive Planner uses a 60-minute tissuecompartment to control its Surface Interval Credit Table because:

if divers dont exceed the NDLs, the slow 120-minutecompartment can be virtually ignored. When Dr. RayRogers developed the conceptual model for the Recreational DivePlanner he realized that recreational (no-decompression) diversalmost never get into situations where the 120-minute compartmentcontrolled their decompression status. Only divers exceeding theNDLs are controlled by such a long compartment. Therefore, hecould base the Recreational Dive Planner surface credit tableon a faster tissue compartment than 120-minutes. The questionwas which compartment to use. Through computer analysis hedetermined that a 60-minute compartment was sufficient to control

over 98% of all recreational dives. To provide for all possibilities including extended no-decompression bottom times at shallowerdepths the special rule for multiple repetitive dives wasdeveloped (WXYZ rule).

Objective 5.2

Explain what is meant by a multitissue decompression model, and state the numberof tissue compartments used in the creation of the Recreational Dive Planner versusU.S. Navy models.

1. The tissue compartments considered within a decompressionmodel are related directly to specific tissues of the body.False. This is a very common misconception regarding divetable design. Tissues compartments are simply mathematicalconcepts. They are not intended to relate one-for-one to actualbody tissues. In fact, physiologists who design dive tablesprefer the term compartmentover tissueas a way of avoidingthis misconception. Dividing the body into compartments isjust a way of describing and predicting what is likely to occurregarding the decompression status. In fact, no one even knowsif any conceptual model used to construct a dive table has any

actual physiological basis.





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2. If the human body is made up primarily of water, why cantdecompression theory be simplified by using a single-tissuemodel?Although the human body is made up primarily of waterour tissues are highly complex as compared to simple water. Theamount and time required to absorb gas is dependent upon twofactors: the type of tissue involved and the amount of blood flowto the tissue. This makes constructing a decompression modelfor humans far more difficult than describing gas absorption/elimination in water. An excellent explanation of the phenomenois provided in the Encyclopedia, Chapter Five, Inert Gas Release Current Theory.

3. (a) In constructing the U.S. Navy tables, 6tissue compartmentswere used to determine the NDLs. In determining the NDLsfor the Recreational Dive Planner, 14tissue compartmentswere used. The Navy constructed their tables almost entirelywithout the assistance of computers. This made the task difficultand time consuming. Using fewer compartments meant lessdevelopment time (although this was still one more than

Haldane used in his original model). The Recreational DivePlanner, on the other hand, was entirely computer-generated.The number of compartments used for calculation was notsignificant in terms of time or difficulty. However, there isntanything innately better about more compartments. In fact, onedecompression model, the Canadian Defense and CivilianInstitute for Environmental Medical (DCIEM) Tables, uses onlyfour compartments

4. While several tissue compartments were used to determine theNDLs for both the Recreational Dive Planner and USN tables,

only one tissue compartment was used to control the gas washout during the surface interval. True. In terms of off-gassing,the slowest compartment controls a subsequent dive. In the caseof the Navy tables, they used the 120-minute compartment.The Recreational Dive Planner uses the 60-minute compartmentto calculate nitrogen elimination. You may wish to look at theresponse to Objective 5.1 as a review of this concept.





Correct:Confident

GuessIncorrect:

Simple MistakeLack of Knowledge

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Correct:Confident

GuessIncorrect:




Objective 5.3

When diving above sea level, explain why it is critical to know the altitude at whichthe dive is to take place.

1. (a) The decompression-related problems encountered whendiving at altitude occur because the diver begins his dive: at an

atmospheric pressure less than that at sea level. TheRecreational Dive Planner was designed for use assuming thedive starts at an atmospheric pressure of 1 atm/14.7 psi. Whilesome reduction in the atmospheric pressure can be tolerated,the Recreational Dive Planner cannot be used at an altitudeabove 300 metres/1000 feet without special procedures. Oneof the most important considerations when diving at altitudeis converting the actual depth of the water at altitude to anequivalent sea-level depth. This conversion is then used for diveplanning purposes. An explanation of why such a conversionis necessary is discussed in Section Three, Objective 3.14. Inaddition, you may also wish to review the related conceptsdiscussed in Section Four of this workbook, Objective 4.8.

2. Because it was designed to allow multilevel diving, there is noneed to convert actual depths into equivalent sea-level depths inorder to the use Recreational Dive Planner at 300 metres/1000 feet above sea level or higher. False. The fact that theRecreational Diver Planner was designed to allow multileveldiving has no bearing on the need to convert altitude depths toequivalent sea level depths.

Objective 5.4Explain why pressure groups from one model/table cannot necessarily be transferredto another model/table.

1. Because they are based on the same theoretical model,pressure groups may be transferred between the RDP Table,eRDP and The Wheel. True. Although the data is displayedin different ways, the model from which all versions of theRecreational Dive Planner were derived is the same. Therefore,in this case it is possible to transfer the pressure groups betweenthe RDP Table, the eRDP and The Wheel. This, however, cannot

be done if the table models differ. For example, although boththe Recreational Dive Planner and the U.S. Navy tables bothuse alphabetic designations for pressure groups, they cannot betransferred from one table to the other. Pressure groups actuallyrelate to a specific amount of nitrogen tension within the bodyas defined by the particular model. As the models differ, somight the particular nitrogen tensions.

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2. Upon exiting the water a diver using the Recreational DivePlanner determines he is in pressure group J. Another diver whis using the U.S. Navy tables also determines that he is in group

J. Is it likely that the two divers have approximately the samedive profile?The diver cannot transfer tables during arepetitive dive. Although both the Recreational Dive Plannerand the U.S. Navy tables use the term J to define a certainamount of residual nitrogen, these exact amounts differ betweethe two models. The scenario in question is a classic case ofadding apples and oranges. Once a dive is initiated using aparticular dive table, that same dive table must be used for anysubsequent repetitive diving.

Objective 5.5

Using the RDP Table or eRDP and The Wheel, demonstrate how to find a no-decompression limit (NDL), and state the procedures for Emergency Decompression andOmitted Decompression.

1. (b) A diver plans a dive to 30 metres/100 feet for 20 minutes.Losing track of time, he notices that his bottom time is actually 2minutes. Which of the following procedures should he institute this situation?Immediately ascend to 5 metres/15 feetand make a stop for 8 minutes; avoid diving for 6hours.The diver has exceeded the no-decompression limit for30 metres/100 feet. However, the overstay has been for lessthan 5 minutes. Had he overstayed the NDL for more than fiveminutes, response A would have been correct. Incidentally, diveshould never be planned to the full limit of the table, and thisscenario is one reason why.

2. (c) A diver plans a dive to 35 metres for 13 minutes/110 feetfor 15 minutes. Upon surfacing he discovers that he misread hitiming device. He was actually at depth for 21 minutes. Whichof the following procedures should he institute in this situation?Remain on the surface, rest, be monitored for signsof decompression sickness, breathe 100% oxygen,and do not dive for at least 24 hours. In this scenario thdiver has exceeded his NDL substantially. The scenario in thisquestion is easily avoided by always taking a safety stop at theend of a dive, double checking your decompression status whil

you wait. If an oversight is discovered the safety stop can thenbecome an emergency decompression stop.





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3. MetricUsing the RDP Table or eRDP, the no-decompression limit for adive to 27 metres is 20minutes.

ImperialUsing the RDP Table or eRDP, the no-decompression limit for adive to 52 feet is 55 minutes.

4.MetricUsing The Wheel, the no-decompression limit for a dive to 27metres is 23minutes. The differences in the NDLs for dives tothe same depth is explained by the fact that The Wheel (in thisexample) uses a depth closer to the actual depth. The Tablerounded to 30 metres while The Wheel only needed to berounded to 28 metres.

ImperialUsing The Wheel, the no-decompression limit for a dive to 52feet is 65 minutes. The differences in the NDLs for dives to

the same depth is explained by the fact that The Wheel uses5-foot depth increments (in most cases). The Table uses 10-foot increments. Therefore, in question 3, the dive had to beplanned assuming a depth of 60 feet. In question 4, the divecould be planned closer to the actual depth of 55 feet.

Objective 5.6

Using the RDP Table or eRDP and The Wheel, calculate dive profiles for three or morerepetitive dives demonstrating the correct guidelines and procedures for: determiningminimum surface intervals; taking safety stops; and applying the special multiple dive rule.

Note: The RDP Table (or eRDP) was used to answer thefollowing questions.

1. (d) A diver exits the water at 10:45 a.m. after a dive to 24metres/78 feet for 21 minutes. At 11:15 a.m. he reenters thewater for a 36-minute dive to 18 metres/60 feet. If he wishes tomake a third dive after only a 2 -minute surface interval, what isthe maximum depth to which he may dive and remain for at least20 minutes?The third dive cannot be made with such ashort surface interval. Anytime you are planning a series ofthree or more dives, be sensitive to the multiple repetitive dive

rule. In this case, a specific surface interval of either 1 hour isrequired even though a much shorter interval could be derivedusing the regular table procedure. Remember, this special ruledoes not apply if you are only making one repetitive dive. As areminder, the rule states, if you are planning 3 or more dives inone day: Beginning with the first dive, if your ending pressure







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group after any dive is W or X, the minimum surface intervalbetween all subsequent dives is 1 hour. If your ending pressuregroup after any dive is Y or Z, the minimum surface intervalbetween all subsequent dives is 3 hours.

Metric Profile

K 30 F W 1 00

3

24 18

21 36

20 36 56

Imperial Profile

K 30 F W 1 00

3

78 60

21 36

19 36 55

2. A diver is planning a dive to 20 metres for 38 minutes/70 feet for 35 minutes. What is the minimum amount of timethe diver would have to spend at the surface if he wished torepeat the exact same profile?2 hours, 31 minutes.If

you did not get that answer you should review the procedurefor finding minimum surface intervals. More information andpractice questions can be found in the PADI Recreational DivePlanner, Instruction for Use (Table version) and in the ElectronicRecreational Dive PlannerInstructions for Use booklets.

Metric Profile

Q 2 31 A T

3

20 20

38 38

6 38 44

Correct:Confident

GuessIncorrect:


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Imperial Profile

Q 2 31 A T

3 3

70 70

35 35

5 35 40

3. (d) A diver is planning a series of 3 dives. Assume he will useminimum surface intervals, follow all Recreational Dive Plannerrules and dive the following exact profiles: Dive 1 - 24 metresfor 26 minute/80 feet for 28 minutes; Dive 2 - 12 metres for85 minutes/40 feet for 80 minutes; Dive 3 - 11 metres for61 minutes/35 feet for 60 minutes. In minutes, approximatelyhow long will the entire dive profile take to completefrom

start to finish?362 minutes. If you indicated response A,you made two mistakes: First, you did not apply the multiplerepetitive dive rule (a three hour surface interval is requiredbetween dives 2 and 3). Secondly, you did not account for tworequired 3-minute safety stops (one after dive 1 and dive 2). If

you selected response B you remembered the safety stops, butnot the multiple repetitive dive rule. If you selected response C,

you remembered the multiple repetitive dive rule, but forgot therequired safety stops.

Metric Profile

O 04 N Z 3 00 A P

3 3

24 12 11

26 85 61

62 85 147

9 61 70



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Metric Profile

P 50 G S 39 J Y

19 17 15

34 24 40

Imperial21 minutes. Lets review this problem using The Wheel. If adiver exits the water at 1:30 p.m. after a dive to 63 feet for34 minutes, he will be in pressure group P. He reenters thewater at 2:20 p.m. This means his surface interval is 50minutes. In 50 minutes a diver in pressure group P changes topressure group G. If he then returns to 55 feet for 24 minutes,he will then be in pressure group R. To make the final dive to50 feet for 40 minutes (using 40 minutes as the NDL), the diver

will be in pressure group M. Therefore, we find that a diver inpressure group R will enter pressure group M in 21 minutes.So the soonest the diver could reenter the water between thesecond and third dives is 21 minutes.

To be conservative, you could use pressure group L (instead ofM) for the final dive to 50 feet for 40 minutes. By using L as thepressure group, you would need to remain on the surface 26minutes in between the second and third dives. Why 26 minutes?A diver in pressure group R will enter pressure group L in 26minutes. More information and practice question can be found inSection Six of The Wheel Instructions for Use and Study Guide.

Imperial Profile

P 50 G R 21 M Y

3

63 55 50

34 24 40

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5. A diver exits the water at 10:40 a.m. after a dive to 28metres/95 feet for 20 minutes. He reenters the water at12:20 p.m. for a dive to 19 metres/65 feet for 27 minutes.How soon could the diver reenter the water for a dive to17 metres/55 feet for 30 minutes?

Metric37 minutes. Lets review the problem. Using The Wheel, a

dive to 28 metres for 20 minutes yields a pressure group ofM. Exiting at 10:40 p.m. and entering again at 12:20 givesthe diver a surface interval of 1 hour and 40 minutes (1:40).A diver in pressure group M changes to pressure group B in1:40. A diver in pressure group B after a dive to 19 metresfor 27 minutes will exit in pressure group Q. To enter thewater for the final dive to 17 metres for 30 minutes, the divermust be in a pressure group no greater than I. Therefore, a Qdiver becomes an I diver in 37 minutes. If you did not get thatanswer you should review the procedure for finding minimumsurface intervals. More information and practice questions can

be found in Section Six of The Wheel Instructions for Use andStudy Guide.

Metric Profile

M 1 40 B Q 37 I W

3 3

28 19 17

20 27 30

Imperial22 minutes. Lets review the problem. Using The Wheel,a dive to 95 feet for 20 minutes yields a pressure group ofN. Exiting at 10:40 p.m. and entering again at 12:20 givesthe diver a surface interval of 1 hour and 40 minutes (1:40).A diver in pressure group N changes to pressure group B in1:40. A diver in pressure group B after a dive to 65 feet for27 minutes will exit in pressure group Q. To enter the waterfor the final dive to 55 feet for 30 minutes, the diver must bein a pressure group no greater than L. Therefore, a Q diver

becomes an L diver in 22 minutes. If you did not get thatanswer you should review the procedure for finding minimumsurface intervals. More information and practice questions canbe found in Section Six of The Wheel Instructions for Use andStudy Guide.



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Imperial Profile

N 1 40 B Q 22 L X

3 3 3

95 65 55

20 27 30

Objective 5.7

State the recommendations for flying after diving and demonstrate its use.

1. (b) A diver exits the water at 10:00 a.m. after a dive to 60feet/18 metres for 50 minutes. He has made no previous dives.What is the soonest this diver should board a commercialairliner for his flight home?10:00 p.m. In this case the diverhas made no previous dives. Therefore, he should wait a

minimum of 12 hours before flying. However, remember thatwhenever possible it is suggested that you wait for an extendedtime beyond 12 hours before flying.

2. (b) A diver has been on a diving vacation for a week, duringwhich he made in excess of twenty dives. He exits the waterat 12:00 noon. What is the soonest this diver should board acommercial airliner for his flight home?After 6:00 a.m. thenext day, the longer the wait the better. In this scenariothe diver has been diving for several days. Therefore, accordingto the recommendations he should wait for a minimum of 18

hours before flying.3. (b) Upon surfacing a diver realizes he has dived the following

profile: 29 metres/95 feet for 23 minutes. What is the soonestthis diver should board a commercial airliner for his flighthome?more than 18 hours after exiting the water.If possible, the diver should wait longer after a dive requiringdecompression or if a decompression stop has been missed before flying or driving to altitude.


Incorrect:






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Objective 5.8

Using The Wheel, demonstrate how to calculate a multilevel dive.

1. (d) During a multilevel dive, a diver spends 10 minutes at adepth of 34 metres/120 feet. If he then wishes to ascend to 26metres/85 feet, what would be his remaining no-decompressio

time during the shallow portion of the dive?The dive cannotbe made as planned as it is outside the allowableparameters for a multilevel exposure.Notice thatthe 34-metre/120-foot curve originates from the yellow boxmarked 24/80. This means that the shallower portion of amultilevel dive from 34 metres/120 feet must be to a depthof 24 metres/80 feet or less. Therefore, ascending to only 26metres/85 feet is not allowed.

Metric Profile

Must be 24 metres or less

26

34 G

10

Imperial Profile

Must be 80 feet or less

85

120 G

10

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3. (d) A diver is planning a multilevel dive. He wishes to stay at34 metres/120 feet for 5 minutes, then ascend to 24 metres/80 feet for 22 minutes. What will his pressure group be uponexiting the water?The dive cannot be made as plannedas it is outside the allowable parameters for amultilevel exposure. Lets review the problem. After a diveto 34 metres/120 feet for 5 minutes the divers ending pressuregroup (EPG) is B. If he then ascends to 24 metres/80 feet hisnew NDL for that depth is 20 minutes. Remember, on shallowerportions of a multilevel dive the bottom time is limited by theML mark on the curve. The diver cannot go to the full NDLmark at the end of the curve. In this case, 22 minutes wouldexceed the ML mark.

Metric Profile

24

22

34 B

5

Beyond multilevel (ML) limit - cannot make dive as planned.

Imperial Profile

80

22

120 B

5

Beyond multilevel (ML) limit - cannot make dive as planned.

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Section AnalysisFrom the answer key, identify any items marked "correct-guess" or "incorrect-lack ofknowledge." These items represent important points of information or concepts you still might

not fully understand. Check below any objectives that contained items with a "correct-guess"or "incorrect-lack of knowledge" response. Completing this section is an important step indetermining your understanding of the RDP as it relates to recreational diving.

Confident Guess Total

Correct Responses

Simple Mistake Lack of Knowledge Total

Incorrect Responses

Objectives To Be Reviewed:

5.1 5.2 5.3 5.4

5.5 5.6 5.7 5.8

0

0

0 0

0 0

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DKW_5_RDP