Dive Equipment & Technology Flashcards

What is a dive computer's 'no-decompression limit' (NDL) display and why is it critical for divers?

Answer: The remaining time a diver can stay at current depth without incurring a decompression obligation

The NDL display shows the remaining time at current depth before mandatory decompression stops would be required — when it reaches zero, the diver must begin ascending.

What is the purpose of the 'dump valve' on a BCD?

Answer: To rapidly release air from the BCD, used during ascent to prevent uncontrolled rise

Dump valves allow divers to rapidly release air from the BCD to slow an ascent or vent expanding gas during ascent — they are essential for buoyancy control.

What is enriched air nitrox and what are its key advantages and limitations compared to standard air?

Answer: A breathing mixture with higher oxygen content than air, offering longer NDLs but with an oxygen toxicity risk and maximum depth limit

Enriched air nitrox contains more oxygen than standard air (typically 32% or 36% O2), which reduces nitrogen content and extends no-decompression limits, but imposes a maximum operating depth due to oxygen toxicity risk.

What regular maintenance is required for a scuba regulator to ensure safe performance?

Answer: Annual or manufacturer-specified service by a qualified technician, plus fresh water rinsing after every use

Regulators require professional servicing at manufacturer-specified intervals (typically annually or every 100-200 dives) and fresh water rinsing after each use to prevent salt and corrosion damage.

What is the purpose of a surface marker buoy (SMB) and when should it be deployed?

Answer: To signal the diver's position at the surface during ascent or after surfacing, especially in areas with boat traffic

An SMB (safety sausage) is an inflatable signal device deployed during ascent or at the surface to alert boat traffic and surface support of the diver's location.

What is the difference between a 'piston' first stage and a 'diaphragm' first stage regulator?

Answer: Piston stages use a moving piston to reduce pressure; diaphragm stages use a flexible membrane isolating internal parts from water, making them preferable in cold or contaminated water

Piston first stages use a moving piston directly exposed to water; diaphragm types use a flexible membrane that isolates the internal mechanism from water, making them better in cold or contaminated conditions.