Which of the following units of pressure are considered absolute values?

The correct answer is PSIA because it represents pressure measured relative to a complete vacuum, making it an absolute measurement. In terms of pressure, absolute pressure is the total pressure exerted, including the atmospheric pressure surrounding a system. This is crucial in engineering applications where knowing the true pressure value is necessary for calculations involving fluid dynamics, thermodynamics, and other related fields.

In contrast, PSI (pounds per square inch) is a general measure that can refer to either absolute or gauge pressure depending on the context. PSIG (pounds per square inch gauge) specifically refers to pressure measured relative to atmospheric pressure, meaning it does not account for atmospheric pressure in its measurement. InHg (inches of mercury) can also be used to describe both absolute and gauge pressure, but without a specific designation, it does not necessarily indicate an absolute measurement. Therefore, only PSIA is consistently recognized as an absolute pressure unit.