Without prejudice to the general obligation imposed by the last foregoing section, where any work done in any premises to which this Act applies is of such a kind that it (or a substantial part of it) can, or must, be done sitting, there shall be provided for each person employed to do it there a seat of a design, construction and dimenstions suitable for him and it, together with a foot-rest on which he can readily and comfortably support his feet if he cannot do so without one.

A seat provided in pursuance of the foregoing subsection, and a foot-rest so provided that does not form part of a seat, must be adequately and properly supported while in use for the purpose for which it is provided.

For the purpose of subsection (1) of this section, the dimensions of an adjustable seat shall be taken to be its dimensions as for the time being adjusted.