Vacuum trap. Simply insert dry ice into the middle section. Intake hose barb is on the bottom and output is near the top. Condensed vapors are dropped into separate flask for collecting large amounts of solvent or volatile compounds. A vacuum trap or "cold trap" is used to prevent vapors from entering your vacuum pump and contaminating your vacuum pump oil. If your vacuum pump ingests vapor it can be detrimental to performance and longevity of the pump. It is crucial to protect your vacuum pump in order to reach and maintain the required vacuum level, and prevent costly and unnecessary oil changes.