An infrared heating unit (2) comprises a housing (6, 8) and a heat resistant, porous ceramic matrix (10) received in the housing having an inner surface (12), side walls (13) and an external surface (14). There is at least one resilient anchoring strip (25) extending between the ceramic matrix and the housing about the perimeter of the ceramic matrix to retain the ceramic matrix in place within the housing and seal the edges of the ceramic matrix. The resilient anchoring strip is adapted to expand or contract to accommodate relative movement of the ceramic matrix with respect to the housing due to heating expansion of the housing.