Certified Hyperbaric Technologist Practice Test

What is the correct procedure to convert feet of seawater (fsw) to ATA?

1. Multiply by 33, then add 1

2. Add 33 to the value

3. Divide by 33, then add 1

4. Subtract 1, then divide by 33

The correct answer is: Divide by 33, then add 1

The conversion of feet of seawater (fsw) to atmospheres absolute (ATA) is based on the principle that 33 feet of seawater is equivalent to 1 ATA. At sea level, 1 ATA represents the atmospheric pressure exerted by the air above. Consequently, to convert feet of seawater to ATA, one must account for the pressure increase due to the weight of the water. To perform the conversion, you first divide the number of feet of seawater by 33 to determine how many atmospheres of pressure are attributed to the water. Then, since atmospheric pressure at sea level contributes an additional 1 ATA, you add 1 to include that baseline pressure. This results in the formula: (fsw / 33) + 1 = ATA. Thus, this procedure accurately reflects the relationship between seawater depth and pressure, aligning with the physical principles of fluid mechanics and gas laws that inform hyperbaric medicine and practices.