Certified Hyperbaric Technologist Practice Test

To convert ATA to PSI, which operation should be performed?

1. Add 1, then multiply by 14.7

2. Multiply by 14.7, then add 1

3. Subtract 1, then multiply by 14.7

4. Subtract 14.7 from the ATA value

The correct answer is: Subtract 1, then multiply by 14.7

To convert ATA (atmospheres absolute) to PSI (pounds per square inch), the correct operation involves subtracting 1 from the ATA value and then multiplying by 14.7. This is based on the relationship between these units, where 1 ATA is equivalent to the atmospheric pressure at sea level, which is approximately 14.7 PSI. When a measurement is given in ATA, starting from the standard atmospheric pressure (1 ATA), any additional atmospheric pressure is then expressed in PSI. Thus, for any ATA greater than 1, you would first subtract the 1 ATA (which is equal to 14.7 PSI) to isolate the excess pressure above standard atmospheric pressure. After that, multiplying by 14.7 provides the pressure in PSI for the additional atmospheres. This method captures the conversion accurately because it properly accounts for the baseline atmospheric pressure of 14.7 PSI and translates the remaining pressure directly into PSI units, which is essential for understanding the pressure differential when working in various hyperbaric environments.