The sodium silicate intumescent material is activated at temperatures of between 100–150°C, forming a rigid foam with a high level of thermal insulation, it expands to 5–10 times its original size.

The intumescent material is activated at a much lower temperature than that at which the smoke seal material degrades. Long before the smoke seal has burned away, the intumescent material has expanded, sealing the gaps around the door. This seals the gap between the door and the frame, so providing an effective barrier to the passage of fire and hot smoke.

The applicable national and international guidelines, standards, approvals and other relevant regulations with regard to smoke control and fire resistance have to be taken into consideration in order to guarantee the fire resisting properties of the element.