Moisture accumulation is normal and, if needed, can be extracted with a cotton swab.
Moisture accumulation is normal when feeding our units with compressed air. When the unit is off, you can undo the nut on the top of the rotameter and use a cotton swab to extract the moisture. Additionally, if you have moisture in the air lines you can disconnect the air line at the block and let the compressor blow the excess moisture out. Lastly, make sure to drain the compressor tank periodically if it does not have an auto drain on it, this will help reduce the amount of moisture build up over time.