Ignition temperature - temperature class

By means of this method, gases and vapours are divided into temperature classes. According to these temperature classes, the surface temperatures in explosion-protected equipment and other technological objects is designed in such a way that ignition by the surface is not possible. In the standard, permissible excess values and necessary safety margins below these standard values are defined in detail.

The permissible surface temperature for those parts of the systems, devices and components accessible to the dust is determined by subtracting 75 K from the value determined using procedure A and by multiplying by 2/3 the value determined using procedure B. The smaller of the 2 values determined in this way corresponds to the lowest permissible surface temperature of the equipment. The surface is the area accessible to the dust, temperature classes are not defined for dust, so that a concrete type of dust must always be assumed. The parameters are made available in comprehensive tables, laboratories determine the values on request, and a small, non-official overview is contained in the following table.