5The opening and closing of all such watertight doors and other contrivances as are mentioned in sub-paragraphs (a), (b) and (c) of paragraph 1 and paragraphs 2 and 4 of this Schedule, and of the closing mechanism of all scuppers having their inboard opening below the margin line, shall be practised once a week and also before the steamer proceeds to sea on any voyage which is likely to last more than a week:
Provided that while the steamer is at sea—
(a)the opening and closing of all such watertight doors, which are in use and are hinged or operated by power, shall be practised daily;
(b)nothing in this paragraph shall be taken to authorise the opening of any watertight door or other contrivance which is required by paragraph 1 of this Schedule to be kept closed.