Local exhaust ventilation

09 July 2019

Local exhaust ventilation (LEV) is used to control exposure to airborne contaminants in the workplace. A local exhaust ventilation system will include one or more inlets (or “hoods”), such as a slot, booth or cabinet, placed around or close to the point of release of the contaminant substance. The hoods are connected, via ducting, to a fan or air mover. The extracted air is cleaned and discharged to the outside atmosphere through a stack. It is a legal requirement that where employees are likely to be exposed to substances or agents that are a risk to their health, steps must be taken to reduce that exposure to as low a level as is reasonably practicable. LEV is commonly used for this purpose, but first you must consider:

  • elimination of the hazardous substances being used or the process which creates them.
  • replacement of hazardous substances with less hazardous alternatives.
  • a reduction in the size of the source.
  • reducing the number of employees involved with the process.
  • modification of the process to reduce the duration or frequency of emission.
  • containment of the process which releases the contaminants.

Wherever possible these alternative measures should be chosen in preference to LEV because they will always be more effective. In many situations though, LEV will be the most practicable solution. Where LEV is installed and used the employer must:

  • ensure that the LEV is maintained in efficient working order.
  • make sure employees know how to use the LEV by providing adequate training.
  • follow the instructions in the User Manual.
  • check the system as required and record details in the Log Book.
  • get repairs done when they are necessary, do not wait for the 14 month inspection interval.
  • arrange for the regular examination and testing of the LEV. In many cases this will be an annual (14 monthly) requirement, though for some specific applications more frequent testing is a statutory requirement. See also ‘Thorough Examination and Testing’.
  • keep examination and test records for at least five years.



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