Local Exhaust Ventilation (LEV) capture dusts, mists, gases, vapour or fumes from work processes to prevent them entering the workplace air so that they cannot be breathed in. Most LEV systems discharge exhaust air outside the building via a filter, which removes the airborne contaminant. However, some LEV systems recirculate the cleaned air back to the workplace. If a recirculating exhaust air filter is not working correctly, or is of the wrong type, then harmful contaminants can be returned to the workplace. If the system fails, it could cause exposure that may result in worker ill health.
The aim of this project was to gather information to help identify knowledge gaps in the selection, use, and maintenance of recirculating LEV systems that are fitted with filters for removing particles. This was carried out by engaging with industry and reviewing national and international standards on particle filtration.
The review of the information gathered, indicates that there may be a number of recirculating LEV systems that are not working effectively, and therefore not controlling worker exposure to harmful contaminants. There were also different interpretations across industry as to what constitutes an adequate and suitable filtration efficiency. Future research could work with stakeholders to provide consistency and greater understanding as to the suitability of recirculating systems in key industries.
This report and the work it describes were funded by the Health and Safety Executive. Its contents, including any opinions and/or conclusions expressed, are those of the authors alone and do not necessarily reflect HSE policy.
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