Fibrous material batts are produced from a mixture of natural and synthetic fibres. A sliver (10) of the fibres is fed through a lapping device (11) onto a moving conveyor to form a continuous mat. The sliver is sprayed with a bonding agent and other optional substances during lapping. The mat is then compressed to a required thickness before curing the bonding agent, and is then cut to form batts of a low density. Resilience and fire retardance properties may be imparted to the fibrous material by including an octaborate salt among the substances sprayed with the bonding agent.