Abstract: A piezo sounder device 100 comprising a piezo sounder 110 and a controller 120, wherein the controller 120 is configured, upon activation of the piezo sounder device 100, to drive the piezo sounder 110 at: a first frequency substantially corresponding to a resonant frequency of the piezo sounder 110 at a first operational temperature; and a second frequency substantially corresponding to a resonant frequency of the piezo sounder 110 at a second operational temperature. Also disclosed is a method 200 of manufacturing the device 100, and a method 300 of emitting a sound 400, 500.

Abstract: Disclosed are breathing apparatus comprising lighting systems. Lighting modules are provided to illuminate in vertical and horizontal directions and to illuminate in a first lighting pattern if the determined status condition is a normal status condition and in a second lighting pattern if the determined status condition is an alert status condition.