Further investigations into the distribution of dust concentrations in the face area

Measurements of respirable dust levels at the P.F.R. collieries since 1971 show that face concentrations have fallen appreciably. The dust distribution pattern along coalfaces is still of concentrations increasing from the intake end towards the return, oftea with peak concentrations in return stables.The ratio of concentrations at control points (70m from face-lines along return roadways) , measured during face working time, to mean concentrations for face-workers, measured over the total time underground, rose from 1.4 to 1. 6 in this period ; the increase was due mainly to a high value at one colliery. Average concentrations in 53 percent of return stables exceeded those at control points but only 62 percent of faces had return stables,,Control point measurements by Lining Department were 17 percent lower on average than those made at the sane collieries by Institute of Occupational Medicine staff; agreement between Institute of Occupational Medicine and Scientific Control measurements was good.Dust concentrations measured by means of SIMPEDS personal dust samplers worn by faceworkers were found to be, on average, 30 to 40 percent greater in intake, rippings and stables than values given by static Type 113A samplers, but 12 percent lower along the face-line. ; in return stables and rippings the two measurements were virtually the same.For an individual, the difference in his dust exposure from one day to another was, in general, greater than the difference between individuals in the same working group. “”