Paragraph 13

(1)

If electric power is being used at a working face and the average of the last six determinations of firedamp content made in pursuance of these regulations at the point on the return side of that face at which such determinations are required to be made exceeds 0·5 per cent. by volume—

(a)

any detector required to be in use at that face by virtue of sub-paragraph (d) of paragraph (1) of the last preceding regulation shall be an automatic detector;

(b)

in the case of a longwall face, at which by virtue of sub-paragraph (a) of that paragraph not less than eight detectors are required to be in use, one out of each complete eight of those detectors shall be an automatic detector.

(2)

Nothing in the last preceding paragraph shall require the provision of more than two automatic detectors at any single-unit conveyor face nor more than four automatic detectors at any double-unit conveyor face.

(3)

If broken working is being carried on immediately adjoining the waste in any part of a mine in the course of board and pillar or a similar system of working and—

(a)

the average of the last six determinations of firedamp content made in pursuance of these regulations on the return side of that part of the mine exceeds 0·5 per cent. by volume; or

(b)

if such determinations are not required to be made, the average of a series of at least six determinations of firedamp content made by an inspector at intervals of not less than fourteen days exceeds 0·5 per cent. by volume (being where more than one such series of determinations has been made the most recent series);

then, in a case in which not less than four detectors are required to be in use in those broken workings, one out of each complete four of those detectors, and, in any other case, one of those detectors, shall be an automatic detector.