Air Preparation Units, commonly referred to as Filter-Regulator-Lubricator (FRL) assemblies, are modular pneumatic treatment systems installed at compressed air supply inlets to clean, regulate, and condition plant air before it reaches downstream actuators and valves. These assemblies capture solid particulates and condensate, stabilize pressure spikes to maintain consistent force output, and mist atomized oil into the airstream to reduce component friction. Key hardware features typically include 5-micron particulate filter elements, pressure-locking adjustment knobs, integrated analog or digital pressure gauges, automatic condensate drain valves, and transparent polycarbonate or metal-shielded sight bowls.