This thermally activated, autonomous fire-extinguishing device is designed for enclosed spaces up to 2000 liters, such as electrical cabinets, control panels, safes, cable trays, and fuel tanks with IP20+ protection. It consists of a polymer tube filled with fluoroketone-based gas-generating fire-extinguishing substance (FK 5-1-12) and mounting hardware, typically metal plates. Installed at the highest point inside the protected volume, it activates at 120 °C, causing the tube to rupture and release the extinguishing agent, effectively stopping flame combustion without human intervention.