HAVS calculator

How the HAVS points system works

Under the Control of Vibration at Work Regulations 2005 there are two thresholds for hand-arm vibration, both measured as a daily exposure averaged over eight hours — written A(8):

• Exposure Action Value (EAV) — 2.5 m/s² A(8), or 100 points. At or above this you must plan to reduce exposure and provide health surveillance for regularly exposed workers.
• Exposure Limit Value (ELV) — 5 m/s² A(8), or 400 points. This is a legal ceiling that must not be exceeded — and HSE warns that routinely working up to it will still cause many workers to develop HAVS.

Each tool contributes 2 × a² × hours points, where a is the in-use vibration magnitude in m/s². Points from different tools simply add together, which is what makes the points system easier to use on site than the underlying A(8) maths.

Getting the inputs right

• Trigger time, not task time. Only the time the tool is actually running in the operator's hands counts — for many jobs that's a small fraction of the time on task.
• Use realistic magnitudes. Manufacturer test values often understate real use; HSE recommends using in-use data where available. The presets in this calculator are indicative typical values only.
• Both hands exposed? Use whichever hand receives the greater vibration — don't average the two.
• Several tools in a shift? Enter each one separately; the calculator combines them into one daily figure, which is how the regulations require multi-tool exposure to be assessed.

Rules of thumb from HSE

Regular use of hammer-action tools for more than about 15 minutes a day, or rotary tools for more than about an hour a day, is enough to need a proper assessment. Tingling or numbness that lasts more than ten minutes after putting a tool down is a warning sign that exposure is already too high.

Source: HSE guidance on hand-arm vibration (hse.gov.uk/vibration/hav) and the Control of Vibration at Work Regulations 2005.