Test severity classes are standardized stress levels designed to simulate the range of electrostatic environments that equipment might encounter throughout its service life. The selection of an appropriate class is a critical step in the verification process, as it ensures that a product is tested for resilience commensurate with its intended operational environment.

Table 2 – Test severity classes

Class 3, which specifies a 6 kV contact discharge and an 8 kV air discharge, is designated as the normal test severity class for protection equipment. As outlined in Annex B of the standard, the choice of a specific class is determined by the anticipated environmental conditions. These conditions are directly linked to the potential discharge voltage, with flooring material and relative humidity being primary factors. For example:

• Class 1 applies to environments where discharge voltage is kept below 2 kV, such as those with floors covered with antistatic material and a relative humidity greater than 35%.
• Class 3 applies where discharge voltage is kept below 8 kV, typical of environments with floors of synthetic material and a relative humidity greater than 50%.

The voltage levels defined by these classes are produced by a highly specified discharge generator with a defined output waveform.