Exam tips

The IMCA supervisor and LST exams test whether you can apply the guidance under time pressure. These tips are about turning what you know into marks.

The format

Exam	Areas and number of questions	Time
Life Support Technician (LST)	Physics 20, physiology 20, chamber and LST practices 40	2 hours
Air Diving Supervisor (ADS)	Physics 25, physiology 25, working practices 50	2.5 hours
Bell Diving Supervisor (BDS)	Physics 20, physiology 20, chamber practices 20, bell operations 40	2.5 hours

Pass rule: 75% overall and at least 70% in every area. A strong practices score cannot rescue a weak physics score. On a 20-question area that means 14 right; on 25 it means 18.

Resits: three attempts in total. The first resit can be booked 30 days after the first attempt. Before a third attempt you wait a year and repeat an approved course, and resits must be within two years. Check the current IMCA D013 and your exam centre before you book.

Core text: IMCA D022 Guidance for diving supervisors. Its physics chapter and self-test questions matter most. All the IMCA documents are in the Documents section for members.

On the day

1. Easy marks first. Answer what you know, flag what you don't, and come back. Don't spend five minutes on one question while easy ones wait.
2. Write the working down. A slip you can see is a slip you can fix.
3. Units before numbers. Bar or mbar, litres or m3, gauge or absolute, degrees C or kelvin.
4. Sense-check. A diver breathing 300 l/min, or a chamber PO2 of 4 bar? Something slipped.
5. Read the wrong answers. Distractors are usually the classic mistakes. Work out which mistake gives each one and you'll often spot the right answer.
6. Watch for NOT and FIRST. "Which is NOT..." and "What is your FIRST action..." questions catch people who read too fast.
7. Don't change an answer without a reason. First instinct is usually right unless you've found an actual error.
8. Know your calculator. Brackets round the top and bottom of every fraction; check that ln 10 = 2.303. The venue sets calculator rules, so ask when you book.

The classic traps

• Gauge vs absolute. Gas laws and partial pressures use absolute (depth/10 + 1). Cylinder contents and chamber pressurisation gas use gauge.
• Kelvin. Charles' law only works in kelvin (C + 273).
• Forgetting the air. When pressurising a chamber from the surface, there's already 0.21 bar of oxygen in it.
• Simple averages. Joining chambers or banks needs a weighted average, not the middle of the two numbers.
• Safety factors. 5 for general lifting, 8 for man-riding.
• The bailout margin. Usable pressure = fill - (absolute pressure + 10 bar).
• Rates. 35 l/min working, 40 l/min emergency, 0.5 l/min metabolic oxygen (0.72 m3 per diver per day), 6 kg soda lime per diver per day.
• The last 10 m. Gas volume doubles between 10 m and the surface: the most dangerous part of any ascent.

The fortnight before

• Work through the revision notes for your exam, area by area.
• Do one area at a time in practice mode until you're consistently over 80%, then move on.
• Do a full timed mock every few days. Track your weakest area and fix it first.
• Learn the formula sheet until you can write it out from memory.
• Two days before, do a final timed mock under exam conditions. Then rest.