Certified Hyperbaric Technologist Practice Test 2026 – Comprehensive Exam Prep

The correct answer is based on understanding how the partial pressure of gases increases as one descends underwater, in accordance with Henry's Law. At sea level, the atmospheric pressure is 1 atmosphere (atm), which correlates to the gas dissolved in someone's blood at that pressure. When a person is at 33 feet seawater (fsw), the pressure increases due to the weight of the water above, contributing an additional 1 atm, leading to a total pressure of approximately 2 atm (1 atm from the atmosphere and 1 atm from the water).

According to Henry's Law, the amount of gas that can dissolve in a liquid is directly proportional to the partial pressure of that gas above the liquid. Therefore, when the pressure doubles from 1 atm to 2 atm, the amount of gas that can be dissolved also doubles.

If a person at sea level has 1.5 liters of dissolved gas, at a pressure of 2 atm (33 fsw), the theoretical amount of gas that would be dissolved is double that amount. Thus, 1.5 liters multiplied by the increase in pressure (2 atm) results in 3.0 liters of dissolved gas.

This framework reflects both the physical principles involved and the direct application