Skip to main content

In preventing exposure to harmful substances in the workplace, there is some consideration on hierarchy of control measures, commencing with the elimination or substitution of the hazard or, where these options are not possible, the hazard must be controlled by engineering means. Local exhaust ventilation system (LEV) is one such engineering control measure. Occupational Safety and Health (Use and Standards Exposure of Chemicals Hazardous to Health) Regulations 2000 have specified requirements in term of design, commissioning, inspection and testing of local exhaust ventilation system.

Related Article

LEV System Inspection

Objective LEV System

LEV is an engineering system designed to protect employees from exposure to hazardous substance. Such as vapour, mist, dust or other airborne contaminants by containing or capturing them locally, at the emission point.

To be effective in protecting the employee(s)

  • it is important to ensure of good design
  • fit for purpose
  • regularly maintained
  • monitor the system’s performance.
LEV System |

LEV System Elements

Most LEV systems have five elements.

  • First is an inlet/enclosure/hood where the contaminant is captured or contained and enters the LEV.
  • Second is ducting which conducts air and the contaminant from the hood to the discharge point.
  • Third is the air cleaner or filter that filters or cleans the extracted air if the systems need air cleaning.
  • Fourthly, the air mover which is the fan and motor that powers the extraction system.
  • The last element is discharge or exhaust, an element that releases the extracted air to a safe place. It is utmost important that the unit in its entirety must be of good design to ensure its effectiveness.

The advantages of LEV systems are it will captured emissions if it is properly positioned and/or well-designed units thus protect the employee from exposure. Beside that, the general supply/exhaust ventilation air volume can be reduced as it is not relied upon to dilute contaminants.

Related Article

Register As Professional Engineer

LEV systems also have drawbacks such as if it is place at improper position, contaminants can be drawn into the operator’s breathing zone and the process. Furthermore emissions drawn into the system must be disposed of safely and without adverse effects on the environment. It is also an additional system to operate and maintain; otherwise it could become an exposure and/or fire hazard. Employees must be properly trained in the system’s correct use, its effectiveness and maintenance needs.


Therefore, in order to make sure that LEV serve its purpose, all the participants, from the designer to end-user need to work together. Meanwhile, to provide an effective system it is important to ensure it is well designed and installed, used correctly and properly maintained.

Leave a Reply