An air dryer's main function is to remove moisture (water vapor) from compressed air, preventing corrosion, freezing, and contamination in pneumatic systems, ensuring equipment longevity, product quality, and operational efficiency by reducing the air's dew point. They work by cooling the air (refrigerated dryers), using absorbent materials (desiccant dryers), or utilizing membranes to separate water, protecting tools and processes from damaging condensation and microbial growth.