NAUI Equipment Use & Maintenance 4

Question 1

When attaching a first-stage regulator to a DIN valve cylinder, which step is critical to prevent cross-threading?

Accepted Answer

Hand-tighten the DIN fitting slowly while ensuring it threads straight

Answer

DIN fittings must be started by hand and threaded straight to avoid cross-threading, which can damage both the regulator inlet and the valve.

Question 2

Why should scuba cylinders never be stored fully empty?

Accepted Answer

Moisture and contaminants can enter and cause internal corrosion

Answer

A small residual positive pressure (typically 200–500 psi) keeps moisture-laden outside air from entering and corroding the interior walls.

Question 3

A diver discovers a small crack in the plastic housing of their dive light before a night dive. What should they do?

Accepted Answer

Remove the light from service until it is properly repaired or replaced

Answer

A cracked housing can flood or implode under pressure, causing total light failure or injury; the equipment should not be used until properly repaired.

Question 4

Which type of valve is found on most modern recreational scuba cylinders in the US and allows easy tank-on/tank-off operation?

Accepted Answer

K-valve (on/off valve)

Answer

The K-valve is a simple on/off valve standard on most US recreational cylinders, replacing the older J-valve with its reserve mechanism.

Question 5

What is the function of the intermediate pressure port on a first-stage regulator?

Accepted Answer

It supplies reduced pressure gas to the second stage and BCD inflator

Answer

The intermediate (low-pressure) port delivers gas reduced to intermediate pressure (typically 120–150 psi over ambient) to second stages and BCD inflators.

(NAUI) National Association of Underwater Instructors Certification Practice Test

(NAUI) National Association of Underwater Instructors Certification Practice Test

NAUI Equipment Use & Maintenance 4