This moisture control tube has characteristics to balance the humidity inside the tube with that outside the tube. If the humidity inside the tube differs from that outside the tube, the moisture control tube penetrates the water vapor from the higher humidity side to the lower humidity side.
The moisture control tube penetrates only the water vapor and rarely penetrates the air. The humidity inside the tube is put in the high humidity status due to the mist generated every exhaust, causing dew condensation.
The moisture control tube penetrates the generated mist from the inside of the tube with a high humidity to its outside with a low humidity to prevent accumulation of water vapor and dew condensation inside the tube.