Hence different materials may be present in the gas stream (e.g., water / solvent / acid or alkali containing gases), the condensation temperature of the material to be condensed must be considered first. Having a cold trap, the material made off (glass or metal) and the geometry of the cold trap play an important role regarding the performance of the cold trap. In order to increase the performance of cold traps, these are sometimes provided with integrated baffles, so that the gas is more swirled in the condensation space and thus better condensation can take place on the cold inner wall of the cold trap.
In general, it should be noted that the liquid used for cooling (LN2 or CO2) should be at least 50 ° C colder than the condensation temperature of the substance that you want to condensate out of the gas stream. If you would like to filter e.g. a solvent such as methanol (melting point -98 ° C) or acetone (melting point -95 ° C) out of a gas stream, you will need LN2 (about -196 ° C) as a coolant to achieve sufficient cooling capacity in the cold trap. For water, the melting point is 0 ° C which means that a mixture of CO2 and acetone (about -77 ° C) would be sufficient for water vapor.