Cb250 – fire door 5 x 1.05m – single plain strips in one small pack (fs157). Firestop intumescent door seals are designed to close the gap between the fire door and frame in the event of a fire thereby preventing the spread of smoke and hot gasses. Once installed our seals can lay dormant for many years only activating when exposed to the rising temperatures and pressures in a fire situation. Firestop’s high performance intumescent core contains intercalated graphite which in the event of a fire expands multi-directionally up to 10-15 times its original size sealing the gap and holding the fire door in place.