S.L. 200.1 Art. 3Permittedperiodof emission of dark smoke.

(1) Emissions of dark smoke from any chimney (not being a chimney of a vessel) for not longer than ten minutes in the aggregate in any period of eight hours, or, if soot-blowing is carried out within any such period, for not longer than fourteen minutes in the aggregate in that period, shall be left out of account for the purposes of article 3 of the Act.

(2) The said periods of ten minutes and fourteen minutes shall be increased -

(a) in the case of a chimney serving two furnaces, to eighteen minutes and twenty-five minutes respectively;

(b) in the case of a chimney serving three furnaces, to twenty-four minutes and thirty-four minutes respectively; and

(c) in the case of a chimney serving four or more furnaces, to twenty-nine minutes and forty-one minutes respectively.

(3) Nothing in the preceding sub-regulation shall authorise -

(a) the continuous emission of dark smoke, caused otherwise than by soot-blowing, for a period exceeding four minutes, or

(b) the emission of black smoke for more than two minutes in the aggregate in any period of thirty minutes.

(4) For the purposes of this regulation, where a single boiler or unit of industrial plant is fired by more than one furnace discharging to the same chimney, all those furnaces shall be deemed to be one furnace.

(5) In this regulation, "black smoke" means smoke which, if compared in the appropriate manner with a chart of the type known at the date of enactment of the Act as the Ringelmann Chart, would appear to be as dark as or darker than shade 4 on the Chart.