This Directive lays down measures and procedures designed to prevent or reduce as far as possible air pollution from industrial plants within the Community. For the purposes of these provisions, “plant” shall mean any establishment or other stationary plant used for industrial or public utility purposes which is likely to cause air pollution. Member States shall require prior authorization to operate plants belonging to the categories listed out in Annex I. Authorization may be issued only when the competent national authority is satisfied that: (a) all appropriate preventive measures against pollution have been taken; (b) the use of plant will not cause significant air pollution, particularly from the emission of the substances referred to in Annex II; (c) none of the emission limit values applicable will be exceeded; and (d) all the air quality limit values applicable will be taken into account.