Article 8 of the PPE directive knows three distinct groups of PPE with different conformity assessment procedures. These are named in the Directive as “Simple design”, “Complex design” and neither of these. For this groups of PPE it is common practice to use the terms category I, II and III respectively.
PPE of simple design where the designer assumes the user can himself assess the level of protection provided against the minimal risks concerned the effects of which, when they are gradual, can be safely identified by the user in good time.
This category shall cover all PPE not mentioned under category I oder category III.
PPE of complex design intended to protect against mortal danger or against dangers that may seriously and irreversibly harm the health, the immediate effects of which the designer assumes the user cannot identify in sufficient time.
See also the Guide to application of the PPE Directive 89/686/EEC (pdf-file).