Abstract: A receptacle made of air-impervious sheet material which is heat-sealable at least on one face thereof. The receptacle has portions with the heat-sealable face of one portion opposed to the heat-sealable face of another. The portions are heat-sealed together forming a seal for the receptacle. The receptacle has a check valve for venting air therefrom for deflation of the receptacle while checking ingress of outside air. The check valve comprises an elongate flat tube of heat-sealable sheet material extending between the portions of the receptacle through the seal from the inside to the outside of the receptacle. The tube has opposed walls with an elongate longitudinal passage between them from one end of the tube to the other. The opposed portions of the receptacle are heat-sealed to the outside of the tube in line with the seal.