To what extent do intumescent fire seals expand in the door edges and does a 15mm wide seal expand to a greater extent than 10mm?

To what extent do intumescent fire seals expand in the door edges and does a 15mm wide seal expand to a greater extent than 10mm?

Sodium silicate used in fire seals will expand between five and ten times its original size. But it can be difficult to quantify exactly as it will depend on the heat involved. A 15x4 seal can expand by five to ten times. It is not purely a matter of the intumescent seal expanding to fill the gap around the door, as it is generally tested on 3-4mm gaps around the door. This means that the seal expands to create pressure to help clamp the door into the frame to hold it in place for the required length of time. For this reason larger gaps around existing doors need to be reduced to the tested gap size of 3-4mm. Sodium silicate intumescent material begins to expand at around 100c which will be in the first few minutes of the fire.