What does the term "face velocity" refer to?

The term "face velocity" specifically refers to the speed of the air as it approaches the filter face. This measurement is crucial in the context of air filtration, as it impacts the efficiency of the filter and its ability to capture airborne particles. Higher face velocities can lead to increased airflow but may reduce the filter's effectiveness, as particles may pass through without being captured. Understanding face velocity helps in the proper selection and application of filters in various HVAC systems, ensuring optimal performance based on air handling requirements.

The other options relate to different concepts that are not aligned with the definition of face velocity—overall production speed is irrelevant to air filtration, pressure deals with the force exerted by air rather than its speed, and temperature pertains to the thermal characteristics of the incoming air rather than its velocity.