Abstract: A gate seal for a knife gate valve comprising a sealing surface lining the gate channel and an integral gasket for compression between valve body halves, a chest seal for a knife gate valve comprising a body having an expandable sealing surface and one or more injection chambers adapted to receive an injectable packing, each chamber having a cross-sectional area that is completely surrounded by the body member, and/or a knife gate valve comprising one or both such seals. The chest seal body may comprise a knife gate slot that is peripherally surrounded by the body. The gate seal and the chest seal may comprise a single integral elastomeric member or separate components.