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COSHEM: Physical hazards (noise, vibration, thermal stress, radiation)

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Physical hazards (noise, vibration, thermal stress, radiation)

What this domain tests

This domain - physical hazards including noise, vibration, thermal stress and radiation - tests the physics and health effects, action levels, exposure metrics and control selection. Expect noise dose calculations, vibration metrics and radiation protection principles.

Core rules

  • Noise. The common occupational action level is 85 dB(A) over 8 hours, with a 3 dB exchange rate: each 3 dB increase halves permitted duration. A peak action level, often around 135–137 dB(C), also triggers action. Controls are engineering first, then organisation, then hearing protection. Audiometry detects early hearing loss.
  • Vibration. Hand-arm vibration is expressed as A(8); action and limit values are often 2.5 and 5 m/s2. Whole-body vibration uses a different metric and health outcome. Reduce exposure through tool selection, low-vibration work methods, breaks and maintenance.
  • Thermal stress. Heat assessment uses WBGT, metabolic rate and clothing. Controls include acclimatisation, water, rest, shade, scheduling and cooling. Cold stress risks include hypothermia, frostbite and impaired dexterity.
  • Radiation. Ionising radiation follows ALARA and dose limits; protection is time, distance and shielding. Non-ionising radiation includes ultraviolet, laser and radiofrequency sources, each with different exposure limits.

Worked example

A worker spends 4 hours at 90 dB(A) and 4 hours at 80 dB(A). Using a 3 dB exchange rate and 85 dB(A) as the 8-hour reference, 90 dB is 5 dB above the reference, so 8 hours at 90 dB would give a dose of about 3.17. Four hours gives about 1.59. At 80 dB, 5 dB below the reference, 8 hours gives about 0.315, so 4 hours gives about 0.158. Total dose is about 1.75, or 175 percent, above the action level. A 5 dB exchange rate would wrongly give a lower dose. The correct response is to reduce noise at source, then review exposure duration and hearing protection zones.

Traps that cost marks

  • Using a 5 dB exchange rate for occupational noise.
  • Confusing sound pressure level with dose or forgetting A-weighting.
  • Ignoring peak noise and impulsive sources.
  • Adding vibration from different tools arithmetically instead of using energy summation.
  • Assessing heat by air temperature alone and ignoring humidity, radiant heat and clothing.
  • Mixing radiation dose units such as Gy, Sv and Bq.