law: 19. Power to enter.-
  Subject to any rules made in this behalf, any officer of the Board generally or specially authorised by the Board in this behalf may, at all reasonable times, enter upon any land or premises and there do such things as may be reasonably necessary for the purpose of lawfully carrying out any works or of making any surveys, examination or investigation, preliminary or incidental to the exercise of any power or the performance of any function by the Board under this Act:
  Provided that no person shall enter into any building or upon any enclosed court or garden attached to a dwelling house, unless with the consent of the occupier thereof, without previously giving such occupier at least seven days' notice in writing of his intention to do so.