In many applications, cryogenically cooled baffles are positioned within a fluid conduit to trap gases, particularly water vapor, and thus remove the gases from the flowing fluid.  For example, although diffusion pumps are very efficient at removing many gases from the environment to create a vacuum, they are not efficient in pumping water vapor.  Therefore, it is common practice to position a cold trap in-line ahead of the diffusion pump to remove the water vapor as the remainder of the gases in the fluid are drawn by the diffusion pump.  Similarly, cold traps are used in-line ahead of other vacuum pumps such as turbomolecular pumps.