The invention relates to a caulking or filling device having fire-break properties and made of an elastic material comprising polyurethane foam. The foam is obtained by reacting at least one polyol having a molecular weight of 4000 to 7000 g/mol and an OH index of 20 to 40 (mg KOH/g), and an isocyanate in the form of a prepolymer or quasi-prepolymer comprising between 5 and 25% of free NCO functions.The elastic material comprises at least 50 wt % of flame-retarding agents. The invention also relates to the use of the device for making seals or fillings having fire-stopping characteristics.