What primarily causes moisture to form in the air brake system?

Moisture formation in an air brake system is primarily caused by the compression and subsequent cooling of air. When air is compressed in the system, its temperature increases due to the properties of gas physics. However, as this compressed air is released into the system and is allowed to expand, it cools down. The cooling of the air can cause the moisture contained within it to condense into water droplets, which can accumulate and lead to issues like freezing in cold temperatures or corrosion within the brake components.

In this scenario, while exposure to cold temperatures may contribute to problems related to moisture, it is the process of compression and cooling that is central to why moisture is generated in the first place. Insufficient maintenance of the system and use of low-quality air brakes may exacerbate existing problems or create inefficiencies, but they do not directly cause the condensation of moisture in the air brake system. Understanding the mechanical principles of air compression helps clarify the specific cause of moisture formation.