Hurled like a hand grenade into the flames, a glass “bomb” bursts and drenches the fire with liquid that becomes a smothering gas, harmless to rugs, fabrics and papers but a powerful agent against flames. Besides its usefulness as a hand-extinguisher, it has an automatic feature that makes it a “robot” watchman. In its non-rusting metal handle is a coil spring held by a fuse; when heat melts the fuse, the spring throws a projectile against the glass, breaking it and releasing the fluid,