Fire doors are fitted with intumescent strips in a groove on every edge of the door or fire door frame. When a fire breaks out, the heat causes the intumescent strips to expand to fill the gap between the fire door and the frame. This seals the room and stops the spread of fire for a given time.
If you want to know more about our fire door product, please contact us on alibaba https://dljfz.en.alibaba.com/?spm=a2700.galleryofferlist.0.0.4d611f5deOdayq
