Any power conferred by this Act or regulations [F1 or health and safety regulations which expressly apply to all mines, any class of mine or a particular mine] onF2 the Executive or an inspector to grant, give or impose an exemption, consent, approval, authority, direction, requirement, prohibition or restriction or to make a determination shall be construed as including a power exercisable in the like manner and subject to the like conditions, if any, to vary or revoke the exemption, consent, approval, authority, direction, requirement, prohibition, restriction or determination.

Any exemption, consent, approval or authority granted or given under this Act or regulations [F1 or such health and safety regulations] byF2 the Executive, or by an inspector exercising any function conferred on him under section 120(3), may (subject to any express provision of this Act or regulations [F1 or such health and safety regulations]) be without limit of period or limited so as to expire on a specified date unless renewed, and may be absolute or conditional.