TDI Advanced Trimix Exam
Student’s Name________________________________________Date_______________
Instructor’s Name_______________________________________Score_____________
……………………………………………………………………………………………..
1. What should each member of a dive team put together for deep diving (buy into?)
2. What is the technical diver’s credo?
3. Identify the hazards of breathing an hypoxic trimix on the surface, and what method you
feel is best for handling those hazards.
4. Describe in point form the recommended procedure for getting the most accurate
readings from a “standard” oxygen / helium analyzer
5. If you were planning a dive to a depth where the ambient pressure was 7.47 ata what
percentage helium would be required in the mix if an oxygen partial pressure of 1.3 ata
and an equivalent nitrogen depth of 30 m / 100 ft had been identified as appropriate
working levels?
6. START and STOP are two acronyms designed to make diver’s perform systematic
checks before a dive and before making their ascent from a dive. What do the initials
stand for?
START
STOP
S____________________________
S____________________________
T____________________________
T____________________________
A____________________________
O____________________________
R____________________________
P____________________________
T____________________________
7. Who is responsible for assessing and monitoring your fitness to conduct an advanced
trimix dive?
8. There are five factors we can use to identify a week or disadvantaged diver during dive
planning. One of these factors is a diver who is the least experienced in the current
conditions for the dive. What are the other four?
1.________________________________________________________________
2.________________________________________________________________
3.________________________________________________________________
4.________________________________________________________________
9. (Metric) Three divers are planning their useable gas volumes for a dive. Two divers have
identical double cylinders containing approximately 6400 litres of bottom mix. The third
has double 14-litre cylinders pumped to 220 bar. What would be a workable volume for
the team to adopt as “thirds” ( point at which to turn their dive)?
(Imperial)Three divers are planning their useable gas volumes for a dive. Two divers
have identical double cylinders containing approximately 240 cubic feet of bottom mix. The
third has double 95 cu ft cylinders filled to 2400 psi. What would be a workable volume for
the team to adopt as “thirds” (point at which to turn their dive)?
10. Using the workable gas volume calculated in question 9, how many minutes into their
dive could the team expect to be before reaching the turning point if the depth of the dive
is to be 75 m / 240 ft, with a dive factor of 2 and SAC rate of 14 1/min / 0.5 cu ft / min?
11. What factors might dictate the use of a third decompression gas for an advanced trimix
dive?
12. What three-stage process should every diver engage in when beginning the dive
planning process?
13. “Comfort Zone” is described in the Advanced Student Manual as a “planning tool” to
make sure dives are conducted within what three limits?
14. What are the five ascent waypoints described as being common for all dives and what
additional waypoints are normal for a staged decompression dive?
15. How can divers weigh the odds in their favor with regard to avoiding decompression
ailments and what is the best way to prevent decompression sickness?
16. Environmental issues and the operational parameters of a dive will affect equipment
choices, but there are seven points that your textbook cites as basic rules common to all
kit. One is to back up only what is necessary. What are the other six?
1.____________________________________________________________
2.____________________________________________________________
3.____________________________________________________________
4.____________________________________________________________
5.____________________________________________________________
6.____________________________________________________________
17. What must be marked clearly on each diving cylinder taken into the water?
18. How would one determine the thing marked in question 17?
19. Which bleeds gas fastest at 60 m / 200 ft: a ruptured low-pressure hose, a ruptured highpressure hose, a free-flowing regulator, a ruptured burst disk?
20. If a member of your team is moving their dive light rapidly up and down and from side to
side, what are they “asking” you for?
I have reviewed this exam with my instructor and fully understand any questions
I may have answered incorrectly. Furthermore I declare that I fully understanding the
requirements of this TDI Advanced Trimix Program and agree with the operational limits
described by this TDI course.
_______________________________________
Student signature
_________/ ________/ ___________
date
(mm/ dd/ yy)
_______________________________________
Instructor signature
_________/ ________/ ___________
date
(mm/ dd/ yy)
TDI Advanced Trimix Exam Answer Key
Student’s Name________________________________________Date_______________
Instructor’s Name_______________________________________Score_____________
……………………………………………………………………………………………..
1. What should each member of a dive team put together for deep diving (buy into?)
Every Team member should buy into the team concept
2. What is the technical diver’s credo?
Any diver can call any dive at any time at any reason without fear of
reproach
3. Identify the hazards of breathing an hypoxic trimix on the surface, and what method
you feel is best for handling those hazards.
The major hazards revolve around the inability of an hypoxic mix to support
consciousness at surface ambient pressures. Methods to handle hypoxic mixes
should include appropriate labeling and storage and the use of travel mixes to a
depth at which the hypoxic mix has become normoxic or, better yet, hyperoxic.
4. Describe in point form the recommended procedure for getting the most accurate
readings from a “standard” oxygen / helium analyzer
Follow a set procedure
Make sure flow rate is within operational limits of sensor
Calibrate oxygen sensors with a known gas at same temperature and
relative humidity as unknown gas
Cross-check whenever practical with a second sensor
5. If you were planning a dive to a depth where the ambient pressure was 7.47 ata what
percentage helium would be required in the mix if an oxygen partial pressure of 1.3 ata
and an equivalent nitrogen depth of 30 m / 100 ft had been identified as appropriate
working levels?
For a dive to 7.47 ata the oxygen and nitrogen partial pressures will be 1.3
and 3.16 ata respectively, totaling 4.46 ata leaving 3.01 ata of vacant
pressure to be filled with helium. To express this as a percentage divide it
by the total pressure: 3.01/7.47=0.4029… with is 40%
6. START and STOP are two acronyms designed to make diver’s perform systematic
checks before a dive and before making their ascent from a dive. What do the initials
stand for?
START is: S-Drill; Team check; Air (gas) check; Route; Tables (schedule
and contingency).
STOP is: Schedule (decide which planned schedule is the best to use);
Team (everyone present and accounted for); Orientation (exit route is
clear); Proceed (begin ascent at prescribed speed and with appropriate
stops)
7. Who is responsible for assessing and monitoring your fitness to conduct an advanced
trimix dive?
It is the personal responsibility of each diver to monitor and access their
personal fitness.
8. There are five factors we can use to identify a week or disadvantaged diver during dive
planning. One of these factors is a diver who is the least experienced in the current
conditions for the dive. What are the other four?
They are: Challenged by the environment
Challenged by gas volumes
Challenged by physical limits
Learning or under mentorship.
9. (Metric) Three divers are planning their useable gas volumes for a dive. Two divers have
identical double cylinders containing approximately 6400 litres of bottom mix. The third
has double 14-litre cylinders pumped to 220 bar. What would be a workable volume for
the team to adopt as “thirds” ( point at which to turn their dive)?
Third diver has 6160 Litres of mix and therefore has the volume of gas to
be used in all calculations. To make things easy, hold 160 litres as a small
reserve and divide 6000 by 3 to arrive to 2000 litres. This is useable volume
for thirds among the whole team.
(Imperial)Three divers are planning their useable gas volumes for a dive. Two divers
have identical double cylinders containing approximately 240 cubic feet of bottom
mix. The third has double 95 cu ft cylinders filled to 2400 psi. What would be a
workable volume for the team to adopt as “thirds” (point at which to turn their dive)?
Third diver has approximately 185 cu ft of mix and therefore has the
volume of gas to be used in all calculations. To make things easy, hold 5 cu
ft as a small reserve and divide 180 by 3 to arrive to 60 cu ft. This is useable
volume for thirds among the whole team.
10. Using the workable gas volume calculated in question 9, how many minutes into their
dive could the team expect to be before reaching the turning point if the depth of the dive
is to be 75 m / 240 ft, with a dive factor of 2 and SAC rate of 14 1/min / 0.5 cu ft / min?
Metric: 2000 litres would last slightly longer than 8 minutes
(SACx2x8.5ata=14x2x8.5=238 l/min…2000/238=8.4 minutes)
Imperial: 60 cu ft would last about 7 minutes (SACx2x8.5 ata=0.5x2x8.5=
=8.5 cu ft/min…60/8.5=7.05 minutes)
11. What factors might dictate the use of a third decompression gas for an advanced trimix
dive?
Always balance additional tasks loading and operational complexity
against safety, optimal decompression, contingency planning and
requirements for travel gas (hypoxic gas mix).
12. What three-stage process should every diver engage in when beginning the dive
planning process?
Risk Identification; Risk Assessment; Risk Management or Amelioration.
13. “Comfort Zone” is described in the Advanced Student Manual as a “planning tool” to
make sure dives are conducted within what three limits?
The three limits are: Personal; Operational; Experimental limits.
14. What are the five ascent waypoints described as being common for all dives and what
additional waypoints are normal for a staged decompression dive?
Maximum depth or Target Depth; Off-gassing Ceiling; First Deep Stop or
Micro Bubble stop; First Staged Decompression Stop (Safety Stop);
Surface or Surface Interval; Additional waypoints include Gas Switches.
15. How can divers weigh the odds in their favor with regard to avoiding decompression
ailments and what is the best way to prevent decompression sickness?
Dive conservative profiles with controlled ascents within limits set by
algorithm when well-rested, well-hydrated and unstressed. The best way to
prevent decompression sickness is not to dive at all since decompression
is somewhat unpredictable.
16. Environmental issues and the operational parameters of a dive will affect equipment
choices, but there are seven points that your textbook cites as basic rules common to all
kit. One is to back up only what is necessary. What are the other six?
Inspect equipment prior to every dive; Keep equipment simple; Carry only what is
required for the dive; Be Familiar with all equipment; Conform to a norm (for your
team); Be open to change.
17. What must be marked clearly on each diving cylinder taken into the water?
The Maximum Operating Depth of the gas contained in the cylinder must be
marked clearly on the neck of the cylinder.
18. How would one determine the thing marked in question 17?
Using an oxygen analyzer and a calculator.
19. Which bleeds gas fastest at 60 m / 200 ft: a ruptured low-pressure hose, a ruptured highpressure hose, a free-flowing regulator, a ruptured burst disk?
A ruptured burst disk will bleed gas slightly more rapidly than a ruptured
low-pressure hose, at about twice the rate of a freeflowing regulator, and
about twenty times more rapidly than a ruptured high-pressure hose.
20. If a member of your team is moving their dive light rapidly up and down and from side to
side, what are they “asking” you for?
They are asking for your attention….NOW!!!
I have reviewed this exam with my instructor and fully understand any questions
I may have answered incorrectly. Furthermore I declare that I fully understanding the
requirements of this TDI Advanced Trimix Program and agree with the operational limits
described by this TDI course.
_______________________________________
Student signature
_________/ ________/ ___________
date
(mm/ dd/ yy)
_______________________________________
Instructor signature
_________/ ________/ ___________
date
(mm/ dd/ yy)