PADI Equipment Knowledge & Maintenance 2 — Questions and Answers
Question 1: What is the primary purpose of a dive computer's ceiling display during a decompression dive?
- Show the shallowest depth you may safely ascend to (Correct answer)
- Display remaining bottom time
- Indicate surface interval required
- Alert you when to switch gas mixtures
Correct answer: Show the shallowest depth you may safely ascend to
The ceiling shown on a dive computer is the shallowest depth a diver can safely ascend to without risking decompression sickness.
Question 2: When should a BCD power inflator hose be inspected for internal corrosion?
- During every annual service or whenever salt crystallization is visible on fittings (Correct answer)
- Only when the inflator fails to function
- Every five years during manufacturer overhaul
- After each 50 dives logged
Correct answer: During every annual service or whenever salt crystallization is visible on fittings
Salt crystal buildup on inflator fittings signals potential internal corrosion, and the hose should be inspected during every annual service.
Question 3: What happens to a wetsuit's thermal insulation as a diver descends deeper?
- Insulation decreases because neoprene compresses under pressure (Correct answer)
- Insulation increases due to increased water pressure trapping heat
- Insulation remains constant regardless of depth
- Insulation improves because cold water is denser
Correct answer: Insulation decreases because neoprene compresses under pressure
Neoprene neoprene cells compress under increasing water pressure, reducing the suit's thickness and its thermal protection.
Question 4: A regulator second stage that constantly frees flows underwater most likely has which problem?
- A damaged or improperly seated demand valve or exhaust valve (Correct answer)
- A clogged high-pressure port
- An over-tightened first stage yoke screw
- A cracked second stage housing
Correct answer: A damaged or improperly seated demand valve or exhaust valve
Continuous free-flow from a second stage typically indicates a faulty demand valve or exhaust valve that is not sealing properly.
Question 5: What material are most modern scuba cylinder valve seats made from, and why?
- Nylon or PEEK polymer, because they resist corrosion and provide a reliable gas-tight seal (Correct answer)
- Stainless steel, because it withstands high pressure impacts
- Rubber, because it is soft and conforms to the valve body
- Brass, because it is the same material as the valve body
Correct answer: Nylon or PEEK polymer, because they resist corrosion and provide a reliable gas-tight seal
Nylon or PEEK seats are used because they are corrosion-resistant and form an effective gas-tight seal with the valve pin.
Question 6: When filling a scuba cylinder, why is a slow fill rate preferred over a rapid fill?
- Rapid filling causes heat buildup that temporarily raises pressure, resulting in under-fill when the tank cools (Correct answer)
- Slow filling prevents oxygen from bonding with nitrogen inside the cylinder
- Rapid filling can permanently stretch the cylinder walls
- Slow filling is required by federal law for all scuba cylinders
Correct answer: Rapid filling causes heat buildup that temporarily raises pressure, resulting in under-fill when the tank cools
Fast fills heat the gas, which expands and shows a higher pressure reading; when the gas cools the actual fill is lower than intended.
Question 7: Which feature distinguishes a balanced regulator first stage from an unbalanced one?
- Breathing effort remains constant regardless of tank pressure or depth (Correct answer)
- A balanced first stage delivers gas at a fixed absolute pressure
- Balanced first stages work only with nitrox mixtures
- Balanced first stages eliminate the need for a second stage
Correct answer: Breathing effort remains constant regardless of tank pressure or depth
A balanced first stage maintains consistent intermediate pressure regardless of changes in supply pressure or ambient depth, keeping breathing effort steady.
PADI Equipment Knowledge & Maintenance 2
What is the primary purpose of a dive computer's ceiling display during a decompression dive?