Table 1. The classification standard of health effect grade and working condition grades in occupational hazard risk index method.
| Value | Health effect grade | Working condition grade | ||||
| The content of free silica | Exposure time (h/shift) | No. of exposed workers | Engineering protection measure | PPE usage rate (%)* | ||
| Abberviations: NA=not applicable; PPE=personal protective equipment.
* PPE usage rate: number of workers using protective equipment/number of workers exposed to dust×100%. | ||||||
| 5 | NA | >12 | >50 | None | ≤20 | |
| 4 | NA | –12 | 26–50 | Overall control | 21–50 | |
| 3 | ≥70% | –8 | 16–25 | Partial control, operation but uncertain effect | 51–80 | |
| 2 | 40%–70% | –5 | 6–15 | Partial control, clear effect | 81–90 | |
| 1 | 10%–40% | –2 | –5 | Confined facility | ≥90 | |
| 0 | ≤10% | NA | NA | NA | NA | |