Also known as a cold trap or condenser, it captures gases by condensation on a cooled surface, preventing vapor or liquid from entering the measuring instrument from the system or from the measuring instrument into the system. When gas passes through cold hydrazine, substances with high melting points become liquids, while substances with low melting points pass through, playing a role in separation. It can provide a very low-temperature surface where molecules can condense and increase the vacuum degree by one to two orders of magnitude.