SDI Chapter two- Physics and
Physiology Questions and Answers
Describe the symptoms of DCS, including mild to severe signs and symptoms. -
ANSWER-Minor Signs: A rash/ crackling skin and joint pain are the most common
signs.
Major Signs: Difficulty breathing, dry cough, dizziness, numbness, tingling, paralysis,
temporary blindness, unconsciousness, permanent disability, or death.
How many more times dense is the air in a balloon at 4 atm/bar compared to the air
density at the surface? - ANSWER-The air in the balloon will be 4x denser.
How often should a scuba diver equalize during a descent? - ANSWER-Divers need to
equalize at the surface before beginning the descent, and every couple of feet during
the descent.
If a scuba cylinder lasts two hours at sea level, how long will it last at 20 meters (66
feet)? - ANSWER-The cylinder will last 20 minutes.
List at least five factors that can predispose a diver to decompression sickness. -
ANSWER-Repetitive dives, obesity, age, prior illness, and injuries (past or present)
List two possible ways a diver may feel if they become "narked" at depth. - ANSWER-
The two symptoms are extreme euphoria and extreme anxiety.
What is a reverse block? - ANSWER-A reverse block is when air cannot escape freely
from the air space. It can cause pain or discomfort in the ears or sinuses.
What is the absolute pressure (in atmospheres/bars) at 20 meters (66 feet)? -
ANSWER-20 meters (66 feet) equals 3 atm/bars
What is the depth threshold where most scuba divers generally begin to be affected by
nitrogen narcosis? - ANSWER-The threshold is 30 meters (100 feet).
What is the most important rule in scuba diving? - ANSWER-The most important rule in
scuba diving is to breath continuously and to avoid holding your breath.
What is the most serious injury that a diver could suffer from if they hold their breath
upon ascending? - ANSWER-Ruptured lungs
What may indicate that the air in a scuba cylinder is harmful to consume? - ANSWER-If
the smell or taste of the air if off.
