DEKRA clearly explains the topic of "explosion protection" in a video that we link to here (YouTube link).
Since 1 July 2003, EG Directive 94/9/EG and its conformity assessment procedure must be applied to equipment and protective systems intended for use in potentially explosive atmospheres operating at atmospheric pressure and temperature conditions (-20 ° C to -40 ° C) 80 ° C and total pressures from 0.8 bar to 1.1 bar absolute). As the device is understood in the scope of any electrical and non-electrical equipment that represents a potential ignition source. These include lights, cabinets or electrical sensors that can cause ignition by sparks, arcs or hot surfaces. However, the directive also includes clutches, fans, compressors or rotary valves, which may be considered as sources of ignition due to possible hot surfaces or damage due to the sparking of mutually contacting high-speed metallic components.
The requirements for devices intended for use in potentially explosive atmospheres increase from Category 3 to Cat. 2 / M2 to Category 1 / M1. While for Category 3 equipment, the manufacturer can demonstrate conformity through internal production controls, the other categories must have a notified body turned on and their identification number indicated on the Ex-label of the equipment. The devices may undergo individual tests or the conformity of the device with the EG Directive may be demonstrated, for example, by an EG type examination in conjunction with a certified quality system (in conjunction with ISO 9000) of the manufacturer. Chapter 2 of the guideline describes the possible module combinations and the annexes to the guideline describe the modules in more detail.
The second group covered by the directive is protection systems. These include, for example, flame arresters that locally limit an explosion or automatic fire extinguishing equipment. Autonomous protection systems, like devices of category 1 / M1, must be inspected by a notified body.
For devices and protective systems that are not covered by the operating conditions [temperature / pressure] within the scope of the directive, the explosion protection must be demonstrated as part of the risk assessment according to the German Industrial Safety Ordinance.