Local Exhaust Ventilation (LEV) is the standard control measure for dealing with dusts, vapours and fumes which are generated from a point source. The harmful contaminant is extracted at the point of generation using engineered systems to ensure that the direction of the ventilation flow is away the breathing zone of any operators.
LEV is a mechanical system of ventilation designed to remove a specific contaminant from its source, e.g. Welding fume. It consists of the following: a receptor or capture hood; ducting to remove the contaminant; an a irc leaning device, e.g. Filter to remove the contaminant from the air; a fan to ensure an adequate ventilation rate for the contaminant. This will be dependent on the size of the particles and the size of the LEV system; and a discharge point.
LEV is a mechanical system of ventilation designed to remove a specific contaminant from its source, e.g. Welding fume. It consists of the following: a receptor or capture hood; ducting to remove the contaminant; an a irc leaning device, e.g. Filter to remove the contaminant from the air; a fan to ensure an adequate ventilation rate for the contaminant. This will be dependent on the size of the particles and the size of the LEV system; and a discharge point.
Examples of LEVs include:
- Glove boxes
- Fume Cupboards
- Captor Hoods
- Receptor Hoods
Factors that may reduce
the effectiveness of a Local Exhaust Ventilation System (LEV)
The factors that may reduce
the effectiveness of a local exhaust ventilation (LEV) are failure to position
the hood close enough to the source of emission; damaged ducting; blocked,
damaged, unsuitable or incorrectly installed filters; fan inefficiency perhaps
due to wear or corrosion of the impeller blades; inappropriate initial design
that was made further worse due to process changes; unauthorized alternations
such as increasing the number of inlets; a build up of contaminant in the
dusting and a blocked/ obstructed outlet; incorrect settings such as angle of dampers;
scrubber saturation, and a failure to introduce procedures for the regular
maintenance, inspection and testing of the system.
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