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Must Articles 4(1.1), 7(4) and 8 of Directive 97/23/EC of the European Parliament and of the Council of 29 May 1997 on the approximation of the laws of the Member States concerning pressure equipment (OJ 1997 L 181), read in combination with Annex I to that Directive, be interpreted as meaning that they preclude national regulations, such as the contested paragraphs 1.2.4, P9.5.6.9 and P9.5.8.2 of the Greek Technical Regulation for Gas Installations with an operating pressure of up to 0.5 bar, which impose conditions and restrictions as to the installation method used for pressure equipment (gas pipes), such as compulsory ventilation and a ban on underfloor pipe lines, in order to protect persons, primarily from earthquakes, especially where those conditions and restrictions also apply indiscriminately to pipes which, as in this case, have the CE marking and which the manufacturer guarantees can be safely installed and used without complying with the abovementioned conditions and restrictions?

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Or, conversely, must the above provisions of Directive 97/23/ΕC, read in combination with Article 2 of the Directive, be interpreted as meaning that they do not preclude conditions and restrictions as to the installation method used for pressure equipment (gas pipes), such as those at issue in this case?