Herein are disclosed are apparatus and methods for forming firestopped through-penetrations in poured concrete partitions. The apparatus and methods use an intumescent firestop ring that can be used in combination with a removable sleeve. The firestop ring is detachably mounted on the outer surface of the sleeve form, near one end of the sleeve. The sleeve is positioned and concrete poured around it. After solidification of the concrete the sleeve can be removed to provide a through-penetration containing the firestop ring, secured to the solidified concrete. The firestop ring may optionally comprise one or more retainers and/or one or more insulating spacers.