Table 2 Free silica content (%) in air-borne mine dust and the method of working [18]
Mining method | No. of samples | Min. | Max. | Mean | % of samples, > 5% silica |
|---|---|---|---|---|---|
Board and pillar | 29 | 0.1 | 04.6 | 1.2 | Nil |
Long wall (2 mines) | 8 | 0.4 | 12.5 | 2.7 | 12.5 |
Open cast (2 mines) | 16 | 1.1 | 17.4 | 5.3 | 25 |