Occupational Hygiene : Local Exhaust Ventilation

The most common form of control of airborne substances is local exhaust ventilation (LEV). Under the COSHH regulations there is a requirement to assess all LEV systems at regular intervals. This ensures that they continue to perform as originally intended and are effective in minimising risk. If your company have LEV systems, maybe you should as yourself these questions:

• Are you sure they are effective in reducing exposure?
• Are they regularly examined and tested?
• Are the assessments clear and understandable?
• Do you require advice on remedial actions?

The examination and testing of LEV systems is clearly defined in the regulations and associated Codes of Practice, together with the information of equipment, methods, intervals and record keeping.

The Occupational Hygiene Unit of Newcastle Occupational Health and Hygiene has a wealth of experience in this area and has assessed a wide range of systems including small portable fume extractors, open face booths, multi-branch dust extractors and very large blasting and painting halls.

The initial assessment documents the system, recording the details of the fans, filtration, ductwork and intakes, for comparison to the design specification, if available.

The testing stage measures, where possible, the appropriate parameters, including:

• In-line velocities - pitot or hot-wire anemometer
• Face velocities - hot-wire anemometer
• Capture velocities - hot-wire anemometer
• Static pressures - micro manometer
• Clearance rates - timed smoke evacuation

In addition to the numerical data, photographic evidence is used to further illustrate the findings. The results obtained are compared with published data and reviewed in the light of personal exposures to substances hazardous to health to determine their effectiveness.

If any system appears unsatisfactory the Occupational Hygiene Unit will attempt to identify the problem and recommend remedial action to correct the shortfall.

It is now required that the records for LEV examination and testing is retained for at least 5 years. The Occupational Hygiene Unit will supply a comprehensive report and assessment for each system tested in a clear comprehendible format and in compliance with the requirements of COSHH Reg. 9(2).

As these examinations are required at regular intervals a free reminder service is provided to ensure your company has valid assessments at all times.

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