4.—(1) Determinations of the firedamp content shall be made—
(a)by means of apparatus of a type approved for the purpose by the Minister, by a competent person appointed for that purpose by the manager of the mine; or
(b)by means of samples of air taken by a competent person so appointed and analysed within four days of the taking thereof.
(2) In reckoning a period of four days for the purposes of this regulation no account shall be taken of any Saturday, Sunday or day of general holiday.