Smoke control areas

21 Variation of provisions in Articles 18, 19 and 20
The Head of the Department may, with the approval of the Head of the Department of Finance, by order made subject to affirmative resolution—
(a) vary, generally or in relation to cases specified in the order, the amount of repayment referred to in Article 18(1)( a), and make corresponding variations in the appropriate fraction to be used in relation to the amounts recoverable under Article 18(11);
(b) vary the amounts of the contributions referred to in Article 19(3);
(c) extend the provisions of Articles 18 and 19 to any class of new dwelling;
(d) vary or add to—
(i) the works which are referred to in Article 20(1);
(ii) the appliances referred to in Article 20(1), of which the provision is deemed to be the execution of works.C