This Act may be cited as the Clean Air Act 1968.

The principal Act and this Act may be cited together as the Clean Air Acts 1956 and 1968.

This Act shall come into operation on a day appointed by an order made by the Minister, and different days may be appointed under this section for different purposes and, in particular, different days may be so appointed for the coming into operation of the same provision in different areas.

Any order made under subsection (3) above by the Minister may be varied or revoked by a subsequent order made by him.

Any reference in this Act to the commencement of any provision thereof shall be construed as a reference to the day appointed for the coming into operation of that provision or, in the case of a provision which comes into operation on different days in different areas, shall, in relation to any area, be construed as a reference to the day appointed for the coming into operation of that provision in that area.

This Act shall not extend to Northern Ireland.