When can a standard be used for self-certification under the standards route?

When it has been harmonized, i.e. it has been published by CENELEC or ETSI and transposed into a national standard in at least one Member State AND it had been listed in the “Official Journal of the European Communities”.
Note that to use this route, the harmonized standard(s) applied must make a complete provision, i.e. they must cover all aspects of emission and immunity.