The declaration of conformity and the CE marking are the two instruments which allow the free circulation of products within Europe. In fact the need of removal of technical barriers which obstruct the free circulation of products is already established in the " Rome's Treaty" of 1957. Since 1985 many directives specifying properties of products followed the "General Approach", which, besides other issues:  

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• assert the principle according to which the needs of safety, health, and environmental prevention has to be harmonized in Europe;

• affirm that a product which is legally commercialized in a member state can be commercialized also in other members's states;

• fix the essential requirements of health, safety and environmental prevention;

• identify, through harmonized standards, how to satisfy some or all the requirements requested by directive;

• specify that the harmonized standards have to be transponded in national standards.

• assign to manufacturer the responsibility to issue the CE Declaration of conformity and to affix the CE marking;

• introduce the principle of presumption of conformity for the products which are CE marked and which are accompanied by Conformity's Declaration.

From 1993 the directives, written according to the so-called "New Approach", have introduced the modular scheme, which identifies in general principles and procedures for the conformity's evaluation and for the CE markings apposition. The conformity's evaluation can be attested though one or more certifications, according to the referring directive. With the exception of particular modules, all certifications require the involvement of a Notified Body which, according to the provided process, can:

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• verify and approve the conformity to requirements through exams and/or tests on product;

• approve and supervise the system of warranty of the quality of the manufacturer