A pouch (10) comprises a flexible bag (12) having an opening (12a) at one end, and a safety valve arranged inside the bag (12) to substantially prevent the content of the bag (12) leaving through the opening (12a). The valve comprises a first pair of sheets (22) and a second pair of sheets (24) that are bonded together locally at a plurality of spaced-apart primary bonding points (25), and a third pair of sheets (26), the first, second, and third pairs of sheets (22, 24, and 26) being bonded together locally at a plurality of spaced-apart secondary bonding points (27). The distance between the primary bonding points (25) and the distal end of the sheets of the second pair of sheets (24) varies along a transverse axis (Dt) of the bag (12).
