What pressure is generally considered atmospheric pressure?

Atmospheric pressure is defined as the pressure exerted by the weight of the air in the atmosphere at a given location. At sea level, this pressure is typically measured as 14.7 psi (pounds per square inch). This value is based on standard atmospheric conditions as established by the International Standard Atmosphere (ISA).

The significance of 14.7 psi lies in its use as a reference point for calibrating pressure measurements in various applications, including high-pressure boiler systems. Understanding this baseline allows operators to distinguish between gauge pressure (which does not account for atmospheric pressure) and absolute pressure (which does include it).

The other values listed do not reflect the widely accepted standard for atmospheric pressure at sea level. 15.1 psi is generally above atmospheric pressure, while 14.2 psi and 12.5 psi are below it. Hence, 14.7 psi is the correct representation of atmospheric pressure in standard conditions.