128. Large castings may be trimmed and chipped by hand in the moulding and casting rooms, on the condition that a suitable protection be furnished to the cleaners. This suitable protection requires:(a) the use of suitable curtains, partitions or screens to prevent any injury caused by flying chips or particles;
(b) an exhaust system to prevent dust concentrations exceeding the maximum value allowed by the standard entitled Threshold Limit Values for Substances in Workroom Air of the American Conference of Governmental Industrial Hygienists (ACGIH-1972);
(c) the wearing of goggles and protective clothing and the use of breathing apparatus where the other protective methods do not ensure the required protection. The use of self-contained or air-supplied protective breathing apparatus equipped with an automatic device which interrupts or restricts the air supply in the part of the apparatus covering the face is prohibited.