Abstract: A flexible intumescent material which comprises inorganic fibers and flexible organic fibers together forming a predominantly fibrous matrix, an elastomeric binder and an intumescent substance and which has been compressed at a moisture content of less than 5% by weight. The intumescent material may be produced by wet laying an aqueous slurry of inorganic fibers, flexible organic fibers, the intumescent substance and the elastomeric binder onto a water-pervious support, withdrawing water from the slurry to form a sheet, drying the sheet to a moisture content of less then 5% by weight and then compressing the sheet material.