There is described a unit for sterilizing a web of packaging material, the unit having a bath containing a sterilizing agent in which the web is advanced continuously and an aseptic environment containing sterile air, connected to an outlet of the bath, and housing drying means for removing residual sterilizing agent from the web the aseptic environment is divided into two regions by a narrow-section channel, along which the web travels, and which is sized to produce a predetermined difference in pressure between the two regions, and so force air into the channel from the higher-pressure region to the lower-pressure region to dry the web.
