Abstract: There is disclosed a cover structure for use with fermentation and the like containers. The cover structure includes a lower cover having a plurality of layers of strips of material covering the container, with the strip layers angularly oriented to each other. Spaces can be formed between strips, and in one embodiment the second strips are connected along their sides at spaced intervals to form the spaces. This can provide gaps in the sheet covering the container, allowing gases to pass through. Additionally, spacers may be positioned on the lower cover with a further membrane extending thereover. The spacers create passages for collection of gases escaping through the lower cover. Floating gas collectors may also be provided for collection of gases for further treatment. The cover can provide insulation, to a variable degree.