A sulphur dioxide generator (10) is disclosed which comprises two composite sheets (12, 14). First stage release of sulphur dioxide is from a coating (26) of the composite sheet (14). The coating (26) is between a paper sheet (22) and a weldable coating (24). The coating (26) incorporates a substance which, in the presence of moisture, generates sulphur dioxide. Second stage release is from sulphur dioxide generating powder which is in pockets (30). The composite sheet (12) comprises a paper layer (16) and a weldable layer (18). The layers (24, 18) are sealed together along a series of longitudinal and transverse lines to form the pockets (30).