HVAC - EPA Certification Practice Exam 2025 - Free EPA Certification Practice Questions and Study Guide

In HVAC, the two types of pressure that are most commonly referenced are absolute pressure and gauge pressure.

Absolute pressure is a measurement of pressure relative to a perfect vacuum, meaning it includes the atmospheric pressure in its reading. This makes it useful in many calculations and applications where precise pressure measurements relative to a complete vacuum are required, such as when dealing with refrigeration cycles or certain types of gas measurements.

Gauge pressure, on the other hand, measures pressure relative to atmospheric pressure. This means it does not include atmospheric pressure in its measurement, and it is the most common form of pressure measurement used in everyday applications such as tire pressure gauges and many HVAC systems. Gauge pressure is what technicians often refer to when they discuss the pressures in a system, as it reflects the pressure above atmospheric levels.

Understanding the difference between these two types of pressure is critical for HVAC professionals, as it affects system diagnostics, performance evaluation, and safety measures.