Breaking out concrete: noise and vibration on an 11-day job

Calculate the daily exposure. The vibration exposure A(8) is the magnitude multiplied by the square root of (trigger time divided by eight hours):

A(8) = 12 x sqrt(3.5/8) = 12 x 0.661 = 7.9 m/s2

In exposure points, A(8) squared times 100 gives about 630 points.

Interpret against the regulations. The exposure action value is 2.5 m/s2 (100 points) and the exposure limit value is 5.0 m/s2 (400 points). At 7.9 m/s2 he is more than three times the action value and roughly 1.6 times the limit value.

Duties triggered

• Above the action value: assess and record the risk, introduce a programme of technical and organisational measures to reduce exposure, provide information and instruction, and provide health surveillance to those at risk.
• Above the limit value: take immediate action to bring exposure below the limit, identify why it was exceeded, and modify the controls accordingly. The limit assumes the tool is used properly; it cannot be met by instruction alone here, because the trigger time is too long for a tool of this magnitude.
• Health surveillance: two operatives already report tingling and numbness worse at night, which is consistent with early hand-arm vibration syndrome. Refer both to occupational health, keep the records, and report confirmed HAVS or carpal tunnel syndrome under RIDDOR where the criteria are met.

Judgement: no practical control will get a 12 m/s2 breaker down to 5.0 m/s2 at 3.5 hours of trigger time. The exposure must be reduced by cutting trigger time or changing the method, which means challenging the programme, not just issuing gloves. Anti-vibration gloves offer negligible protection at these frequencies and must not be counted as a control.

Assess against the action values. The lower exposure action value is 80 dB(A) and the upper is 85 dB(A); the exposure limit value is 87 dB(A) taking hearing protection into account. Peak values are compared with 135 dB(C) lower, 137 dB(C) upper and 140 dB(C) limit.

At 96 dB(A) Lep,d the crew is 11 dB above the upper action value, which is a fourfold reduction in permissible exposure time. The peak of 139 dB(C) exceeds the upper action value but sits below the limit value. So the duties are: reduce exposure so far as is reasonably practicable, mandatory hearing protection and demarcated hearing protection zones, audiometry, and information, instruction and training.

Reduce at source first. Ask the client and principal contractor about hydraulic bursters, expansive grout, diamond saw cutting with water suppression, or a larger remote-controlled breaker with a lower noise and vibration rating. These remove the operator from the noise rather than protecting him from it, which is why they rank above PPE. Practical additions: acoustic screens around the work area, maintenance of breaker chisels and mufflers, and restricting breaker use to defined hours so other trades are not exposed unnecessarily.

Selecting and verifying protectors. Do not simply issue defenders. Calculate the attenuation needed: 96 dB(A) minus a target of about 80 dB(A) at the ear suggests around 16 dB of real-world attenuation. Use the manufacturer's SNR figures, then deduct for real-world fitting - a common approach is to halve the SNR or use assumed protection values - and check the result sits comfortably above 80 dB(A) at the ear but not so far below that communication and warning signals are lost. Confirm by fit-checking, supervising correct use, and repeating dosimetry inside the protector if there is doubt.

Audiometry: baseline for all four, then regular intervals; refer any threshold shift.

Structure the programme around exposure, not around the tool.

1. Method. Present the client with the arithmetic: at 12 m/s2 and five hours, operatives are at 630 exposure points against a limit of 400, so the current method cannot lawfully continue as planned. Offer alternatives with comparable programme times - burster, saw-cutting, or a larger remote-controlled breaker - and quantify the trade-off in days, not just cost. A live treatment works constrains the method, so ask what the client's own permit conditions allow before proposing.
2. Rotation and trigger time. Break the five hours into separated blocks with non-vibrating work between, and cap daily trigger time per person. Rotation between four people does not reduce individual exposure unless total trigger time falls; make that point explicitly, because it is the common misapplication.
3. Tool and maintenance. Service breakers and chisels; sharp chisels cut faster and transmit less vibration; check the manufacturers' declared vibration values rather than the hire-desk figure.
4. Noise. Demarcate zones, make defenders mandatory at the gate, provide a selection of plug and muff types for fit and comfort, and provide warm, dry storage so protectors are worn in cold weather.
5. Health surveillance. Baseline audiometry and a HAVS questionnaire before day one; refer the two symptomatic men now and do not redeploy them onto breakers pending advice.
6. Information and supervision. A ten-minute briefing on early symptoms and how to report them, backed by a supervisor who stops the job if trigger time runs over.

Winning cooperation: clients respond to programme certainty and to enforcement risk. Frame the conversation as 'this method exposes you to a prohibition notice and a delay', bring the calculation in writing, and offer a workable alternative on the same dates. Escalate to the principal designer if refused, and record the advice given.