Daily exposure A(8) is the time-weighted vibration exposure normalised to an 8-hour reference period. Manufacturers publish vibration emission values for each tool; AMWS uses the higher of the manufacturer figure or HSE's typical-tool table to set trigger-time limits.
| Threshold | Daily exposure A(8) | Required action |
|---|
| Exposure Action Value (EAV) | 2.5 m/s² A(8) | Eliminate or reduce exposure to as low as reasonably practicable; provide information & training; instigate health surveillance under SOP 8.7 |
| Exposure Limit Value (ELV) | 5.0 m/s² A(8) | Must not be exceeded. Where the limit is reached, stop work, reduce exposure (low-vibration tool, shorter trigger time, job rotation); document deviation |
Tool-specific trigger-time guidance (HSE typical values; manufacturer's actual figure overrides if higher):
| Tool | Typical vibration m/s² | Time to reach EAV (2.5) | Time to reach ELV (5.0) |
|---|
| Hand-held breaker (heavy) | 20 | ~7 minutes | ~30 minutes |
| Hand-held breaker (medium) | 10 | ~30 minutes | ~2 hours |
| Disc cutter (petrol, abrasive disc) | 5 | ~2 hours | ~8 hours |
| Compactor / wacker plate | 5–10 | 30 min – 2 hours | 2–8 hours |
| Percussive drill (rotary hammer) | 10 | ~30 minutes | ~2 hours |
| Angle grinder (hand-held) | 4–8 | ~30 min – 1.5 hours | ~2–6 hours |
| Stihl saw / cut-off saw | 5–7 | ~1–1.5 hours | ~4–6 hours |
Symptoms to report immediately: tingling or numbness in fingers; loss of feeling or dexterity; blanching (white) attacks (Raynaud's phenomenon); reduced grip strength; cold-induced symptoms. Early intervention prevents progression to permanent vascular and neurological damage.
Cold-weather rule: HAVS effects are amplified in cold conditions; warm gloves are mandatory below 10°C; trigger-time limits halve below 5°C.