Abstract: The invention relates to an optical wave guide having at least one optical fiber, a protective sheath and connection fittings at the ends. In order for charges entering by diffusion to be dissipated from the surface of the optical fibers, the fibers have an electrically conductive coating which in turn is connected to the connecting fitting and/or to ground.

Abstract: To relieve explosive pressures due to unintended explosion of explosive fluid, for example dust or combustible particle-laden air, such as sawdust, coal dust and the like, or of combustible gases, passing through a conveying duct (2, 5), a chamber is formed with a releasable closure, the inlet duct end (2a) from the inlet conveying duct terminating in the chamber. The chamber is formed by a cylindrical wall structure (3a) surrounding the inlet duct end (2a) with clearance. An explosion and/or flame detector (D) is located to sense an incipient explosion or flame and providing an electrical output signal. The chamber is subdivided into chamber portions, one in communication with the inlet duct end and the other communicating with the outlet from the chamber by a rapid-acting separating arrangement.