Schedule 4 SPECIFIC SUBSTANCES AND PROCESSES FOR WHICH MONITORING IS REQUIRED
| Column 1 | Column 2 |
|---|---|
| Substance or process | Minimum frequency |
| Vinyl chloride monomer. | Continuous or in accordance with a procedure approved by the Health and Safety Commission. |
| Vapour or spray given off from vessels at which an electrolytic chromium process is carried on, except trivalent chromium. | Every 14 days. |