This invention relates to a thin reinforced nonwoven fabric having ridges and grooves for fire blocking an article and articles containing such fabrics. When exposed to heat or flame, the fabric is capable of increasing to a thickness that is at least 1.5 times its original thickness. The fabric comprises an open mesh scrim having a having crimped, heat resistant organic fibers compressed thereon and held in a compressed state by a thermoplastic binder, on which is imparted a ridge and groove structure. When subjected to high heat or flame, the binder in the structure softens, releasing the restrained crimped fibers and any ridges and grooves and allowing the thickness of the fabric to increase.