The Regulation relating to Explosive Atmospheres (Verordnung explosionsfähige Atmosphären, VEXAT) provides for initial and periodic testing in certain defined cases. Electrical plant and mechanical ventilation and extraction systems, for example, must be checked for explosion resistance in areas with explosion hazards exist prior to being put into operation. Before initial operation, the zone delineations as well as the implementation of explosion protection measures must be ascertained. When electrical plant is exposed to extreme conditions (moisture, extremely low or high temperatures, it has to be inspected at regular intervals. Ventilation and extraction systems have to be inspected once a year. These inspections have to be carried out by suitable and competent persons who may be staff members of the company.