Presumption of Conformity (for EMC)

As you may know, the EC New Approach directives (and thus the EMC Directive) do not exactly specify what requirements are to be met. The goal of the directive has been specified in terms of "essential requirements".  

This requires the assessment to cover a number of essential EMC phenomena.

By mandate from the European Commission, European Standardization Bodies such as CENELEC have been granted permission to autonomously declare EMC standards as being suitable for obtaining a "Presumption of Conformity" with the Essential Requirements.

Once an assessment to the letter of such a standard has been completed a founded conclusion about compliance with the Essential Requirements can be drawn

However, Presumption is not Certainty. 

Therefore, one needs to evaluate the tests and requirements from the standard against the essential EMC phenomena and frequency range, to draw a founded conclusion about the standards coverage of essential phenomena.

Normally a test house will fulfill this assessment for you, however, this does not dismiss you from any responsibility and corresponding initiatives.

If your house hold equipment has been tested according to a Harmonized Standard up to 300 MHz, and creates interference  at 350 MHz, and this went unnoticed, the equipment will not comply to the "essential requirements" in spite of having obtained a "presumption of compliance".

The EMC-directive covers the frequency range up to 400 GHz so the appropriate harmonized standard does not adequately cover the essential requirements.