HAVS Time Limits: Trigger Times for Common Construction Tools
What Are HAVS Trigger Times?
Trigger time is the maximum duration a worker's hands can be on a vibrating tool before they reach an exposure threshold. Every vibrating tool has two trigger times:
- Time to EAV — how long before hitting the Exposure Action Value (2.5 m/s² A(8) / 100 exposure points)
- Time to ELV — how long before hitting the Exposure Limit Value (5 m/s² A(8) / 400 exposure points)
These times depend entirely on the tool's vibration magnitude. A low-vibration tool can be used for hours. A high-vibration breaker might hit the EAV in under 10 minutes.
The reference table below gives trigger times for common tools found on UK construction, civils, and landscaping sites. Use it as a quick lookup — but always check the specific vibration magnitude for your actual tool model.
Trigger Time Reference Table
| Tool | Typical vibration (m/s²) | Time to EAV (100 pts) | Time to ELV (400 pts) |
|---|---|---|---|
| Angle grinder (4.5", cutting) | 4–6 | 1h 23m – 3h 7m | 5h 33m – 12h 30m |
| Angle grinder (9", grinding) | 6–10 | 30m – 1h 23m | 2h – 5h 33m |
| Breaker, electric (light, <10 kg) | 8–14 | 15m – 47m | 1h 1m – 3h 7m |
| Breaker, pneumatic (medium) | 12–25 | 5m – 21m | 19m – 1h 23m |
| Breaker, hydraulic (heavy) | 10–20 | 7m – 30m | 30m – 2h |
| Chipping hammer | 15–30 | 3m – 13m | 13m – 53m |
| Chainsaw (top-handle, arborist) | 3–5 | 2h – 5h 33m | 8h – 22h+ |
| Chainsaw (rear-handle, felling) | 4–7 | 1h 1m – 3h 7m | 4h 5m – 12h 30m |
| Cut-off saw / disc cutter | 5–9 | 37m – 2h | 2h 28m – 8h |
| Hammer drill (SDS) | 9–20 | 7m – 37m | 30m – 2h 28m |
| Impact wrench | 5–15 | 13m – 2h | 53m – 8h |
| Needle scaler | 10–30 | 3m – 30m | 13m – 2h |
| Plate compactor (walk-behind) | 10–16 | 12m – 30m | 47m – 2h |
| Road roller (walk-behind) | 4–10 | 30m – 3h 7m | 2h – 12h 30m |
| Rotary hammer drill | 8–16 | 12m – 47m | 47m – 3h 7m |
| Scabbler | 20–40 | 2m – 8m | 8m – 30m |
| Strimmer / brush cutter | 4–7 | 1h 1m – 3h 7m | 4h 5m – 12h 30m |
| Tamper / rammer | 12–20 | 7m – 21m | 30m – 1h 23m |
| Vibrating poker (concrete) | 6–12 | 21m – 1h 23m | 1h 23m – 5h 33m |
All times are approximate. Vibration magnitudes are typical ranges — your specific tool may be higher or lower. Check the manufacturer's declared value or the HSE vibration magnitude database for your exact model.
How to Read This Table
Example: A worker using a medium pneumatic breaker at 18 m/s²:
- Exposure points per hour = 2 × 18² = 648 points/hour
- Time to EAV (100 points) = 100 ÷ 648 × 60 = 9 minutes
- Time to ELV (400 points) = 400 ÷ 648 × 60 = 37 minutes
At 18 m/s², this worker hits the action value in under ten minutes of trigger time and the legal limit in just over half an hour. That's not unusual for heavy breaking work — which is why breaker tasks need careful scheduling and rotation.
Why Trigger Time Is Not Shift Time
A common misconception: trigger time measures hands-on-tool time, not shift length. A groundworker might be on site for 8 hours but only has hands on a vibrating tool for 45 minutes total. The exposure calculation uses those 45 minutes, not 8 hours.
Conversely, a worker who uses a breaker "just for a few minutes" at 20+ m/s² can blow through the EAV in under 5 minutes of actual use. Short bursts on high-vibration tools are where exposure limits get exceeded without anyone noticing.
Multi-Tool Exposure: How Points Add Up
Most workers use more than one vibrating tool per shift. Exposure points from each tool add together:
Example shift:
| Tool | Vibration | Trigger time | Points |
|---|---|---|---|
| Angle grinder (6 m/s²) | 6 | 4 hours | 288 |
| Hammer drill (12 m/s²) | 12 | 30 minutes | 144 |
| Total | 4h 30m | 432 |
Total of 432 points — over the ELV. Neither tool alone reaches the legal limit (the grinder gets there at around 5h 30m of solid use; the drill at around 1h 23m), but the combination exceeds it in under five hours of total trigger time.
Use our free HAVS Trigger Time Chart for an interactive lookup, or the HAVS Exposure Calculator to calculate multi-tool exposure for your crew.
What to Do With This Information
For site supervisors
- Print or save this table for quick reference during shift planning
- Before assigning a worker to breaking or compacting work, check the trigger time — if the task needs more time than the tool allows, schedule a second worker to rotate
- Log actual trigger times daily, not estimated averages
For company directors / H&S coordinators
- Use trigger times when writing your HAVS risk assessment — they show which tools are highest risk
- Invest in lower-vibration tool models for tasks with long trigger times (e.g., active vibration reduction breakers)
- Set up daily exposure tracking to catch multi-tool accumulation — this is where limits get exceeded without warning
- Reinforce trigger-time awareness on site with a quick HAVS toolbox talk before high-vibration work
When to act
- EAV reached (100 points): Introduce controls — tool rotation, job rotation, lower-vibration equipment, health surveillance. For the full menu of options ranked by effectiveness, see our guide to HAVS control measures.
- ELV reached (400 points): Stop the worker using vibrating tools immediately for the rest of the shift. Investigate and update your risk assessment.
Sources
This guide is for general information only. It is not a substitute for professional health and safety advice.