Recreational Dive Planner – Metric
Revision Exam With Solved Solutions.
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 - Answer c. 6hours / 12 hours
A 60-minute tissue compartment requires 6 hours to fill or empty completely, while a 120-minute
compartment requires 12 hours.
The term "half-time" is simply a way of representing what is known as an "exponential relationship."
In our discussion of decompression theory it's used to describe how quickly a tissue compartment will fill
or empty.
For example, a tissue compartment described as having a "5-minute halftime" will fill (or empty) half of
the total amount of nitrogen it can 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 five more
96.9% and finally in six half-times (30 minutes total) the compartment is considered full (or empty) at
98.4% of its capacity (mathematically it never reaches 100%).
Therefore, a 60-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).
The U.S. Navy selected the 120-minute tissue compartment to control their "Surface Interval Credit
Table" because
a. they didn't 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 model had to be used.
d. this was the easiest way to account for individual differences in physiology. - Answer b. they were
designing tables that enabled decompression diving.
The U.S. Navy selected the 120-minute tissue compartment to control their "Surface Interval Credit
Table" because they were designing tables that enabled decompression diving. The primary function of
the U.S. Navy Tables was to enable safer decompression diving. They also realized with the advent of
scuba that provisions were necessary for "repetitive diving." This required consideration of how quickly
the diver lost residual nitrogen. To accommodate this the Navy developed a "Surface Interval Credit
Table." To avoid having to develop several such tables to be used according to which tissue compartment
controlled the previous dive, they chose an easier approach — develop only one table based on a single
compartment. Determining which compartment to use was simple. As their tables would provide for
decompression diving — even repetitive decompression dives — they had to use the slowest tissue
compartment in their model; one which would come into play only during decompression dives. That
compartment was the 120-minute compartment, which requires 12 hours to fully in or out gas. This
explains why it takes up to 12 hours to fully out-gas when using the U.S. Navy Tables.
The Recreational Dive Planner uses a 60-minute tissue compartment to control its "Surface 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 don't exceed the NDLs the slow 120-minute compartment can be virtually ignored. - Answer
d. if divers don't exceed the NDL's the slow 120-minute compartment can be virtually ignored.
Revision Exam With Solved Solutions.
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 - Answer c. 6hours / 12 hours
A 60-minute tissue compartment requires 6 hours to fill or empty completely, while a 120-minute
compartment requires 12 hours.
The term "half-time" is simply a way of representing what is known as an "exponential relationship."
In our discussion of decompression theory it's used to describe how quickly a tissue compartment will fill
or empty.
For example, a tissue compartment described as having a "5-minute halftime" will fill (or empty) half of
the total amount of nitrogen it can 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 five more
96.9% and finally in six half-times (30 minutes total) the compartment is considered full (or empty) at
98.4% of its capacity (mathematically it never reaches 100%).
Therefore, a 60-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).
The U.S. Navy selected the 120-minute tissue compartment to control their "Surface Interval Credit
Table" because
a. they didn't 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 model had to be used.
d. this was the easiest way to account for individual differences in physiology. - Answer b. they were
designing tables that enabled decompression diving.
The U.S. Navy selected the 120-minute tissue compartment to control their "Surface Interval Credit
Table" because they were designing tables that enabled decompression diving. The primary function of
the U.S. Navy Tables was to enable safer decompression diving. They also realized with the advent of
scuba that provisions were necessary for "repetitive diving." This required consideration of how quickly
the diver lost residual nitrogen. To accommodate this the Navy developed a "Surface Interval Credit
Table." To avoid having to develop several such tables to be used according to which tissue compartment
controlled the previous dive, they chose an easier approach — develop only one table based on a single
compartment. Determining which compartment to use was simple. As their tables would provide for
decompression diving — even repetitive decompression dives — they had to use the slowest tissue
compartment in their model; one which would come into play only during decompression dives. That
compartment was the 120-minute compartment, which requires 12 hours to fully in or out gas. This
explains why it takes up to 12 hours to fully out-gas when using the U.S. Navy Tables.
The Recreational Dive Planner uses a 60-minute tissue compartment to control its "Surface 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 don't exceed the NDLs the slow 120-minute compartment can be virtually ignored. - Answer
d. if divers don't exceed the NDL's the slow 120-minute compartment can be virtually ignored.
