Abstract: A carpet underlay for a floor carpet, the underlay having a foam base layer having an upper surface, and a cross-linked closed cell polyolefin foam upper layer having a first surface and a second surface, wherein the first surface is bonded to the upper surface of the base layer and the second surface is adapted to contact the carpet in abutment. Preferred foam base layer comprises a polyurethane foam, particularly, chipfoam; and the cross-linked closed cell foam layer comprises polyethylene, polyolefine, polyamide and mixtures, thereof. Apparatus and process of manufacture are provided. The underlay provides improved resistance to odour and toxic vapour penetration from the base foam layer through the carpet into the atmosphere above the carpet.