LEV is a generic term used to describe powered extraction systems which are designed to capture and remove hazardous airborne substances as soon as they are released, for example during operations such as welding, paint spraying or soldering. LEV systems are one of the most common means of preventing and controlling employee exposure to chemicals and other hazardous substances.
The New Guidance – HSG258
In May 2008, the HSE published a new, comprehensive guide to Local Exhaust Ventilation (LEV) aimed at designers, installers and examiners of these systems. In addition free leaflets were made available for employers and employees and a new LEV website was launched.
HSG258 'Controlling airborne contaminants at work: A guide to local exhaust ventilation (LEV)' (ISBN 978 0 7176 6298 2), which replaced HSG37 and HSG54, describes the principles and good practice of deciding on, designing, commissioning and testing LEV and can be obtained from HSE Books.
The new guidance document, available since May 2008, relate to the design and use of dust extraction (LEV) systems, initial assessment and mandatory testing at 14-month intervals. The employers' requirements to ensure satisfactory breathing air quality for the workforce are clearly explained.
The handbook "Controlling airborne contaminants at work" considers the total design of extraction systems, from specification, hood and ducting design through to installation and commissioning. The behaviour of dust and fume is described, with explanations of common processes.
LEV installers and commissioning engineers must be made fully aware of all critical details that may affect performance, particularly in relation to clearing the breathing zone of contaminants. Maintenance engineers must know, for example, the hazards associated with the machine and products in use. They must be provided with, and trained to use, appropriate personal protective equipment. They should know how to assess the LEV system and monitor the effectiveness of extraction hoods, using simple qualitative tests like smoke tubes and dust lamp to observe the effectiveness of dust and fume capture.
LEV examiners performing statutory examination and tests must be familiar with the system and understand how legal requirements apply specifically to the individual installation. Of course, they must have complete performance-related information to be able to compare any results against benchmark figures.