How Does Local Exhaust Ventilation (LEV) Work?
Understanding How an LEV System Protects Your Workforce
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Local Exhaust Ventilation (LEV) is one of the most effective methods of controlling airborne contaminants in the workplace. Instead of allowing hazardous dust, fumes, vapours or gases to spread throughout a building, an LEV system captures them at the point where they are created, helping to protect employees and improve workplace air quality.
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At A-Mac Environmental, we design, install, test and maintain bespoke LEV systems for businesses across Scotland, ensuring every system is designed to remove hazardous contaminants efficiently and comply with current COSHH Regulations.
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The Four Main Parts of an LEV System
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Every LEV system works using four key components:
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1. Capture Hood
The capture hood is the first and most important part of the system.
Its purpose is to collect hazardous contaminants before they reach the operator's breathing zone.
Depending on the application, the capture device may be:
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Flexible extraction arm
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Extraction canopy
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Downdraught bench
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Enclosed cabinet
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Extraction booth
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Machine enclosure
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Vehicle exhaust nozzle
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Fume cupboard
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Correct positioning of the capture hood is essential for effective extraction.
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2. Ductwork
Once contaminants have been captured, they travel through a specially designed ducting system.
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The ductwork transports contaminated air safely to the filtration equipment while maintaining the correct airflow throughout the system.
Correct duct sizing is essential to:
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Maintain airflow
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Prevent dust settling inside the ducts
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Reduce energy consumption
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Improve system efficiency
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3. Filtration System
The contaminated air then passes through filters designed to remove harmful particles.
The type of filter depends on the contaminant being extracted.
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Common filtration systems include:
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Cartridge filters
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Bag filters
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HEPA filters
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Activated carbon filters
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Cyclone separators
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Oil mist filters
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These filters remove airborne contaminants before the cleaned air is discharged or, where appropriate, safely recirculated.
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4. Extraction Fan
The fan provides the power that moves air through the entire system.
It creates the airflow needed to:
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Capture contaminants
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Move air through the ductwork
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Pass contaminated air through the filters
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Discharge cleaned air safely
Choosing the correct fan is critical to ensuring the LEV system performs efficiently and consistently.
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How an LEV System Works – Step by Step
An LEV system follows a simple process:
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Hazardous dust, fumes or vapours are generated during a work activity.
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The capture hood collects the contaminant at its source.
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The contaminated air travels through the ductwork.
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The filtration system removes hazardous particles.
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The extraction fan moves the cleaned air through the system.
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Clean air is safely discharged or recirculated where appropriate.
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Capturing contaminants before they spread is far more effective than relying on general ventilation alone.
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What Can an LEV System Remove?
A correctly designed LEV system can control a wide range of airborne contaminants, including:
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Welding fumes
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Wood dust
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Flour dust
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Metal dust
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Respirable crystalline silica (RCS)
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Vehicle exhaust emissions
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Oil mist
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Paint and solvent vapours
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Chemical fumes
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Pharmaceutical powders
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Plastic dust
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Smoke
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Laboratory contaminants​
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Every application requires a system specifically designed for the substances being generated.
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Why Good LEV Design Matters
A poorly designed extraction system may fail to capture contaminants effectively, leaving employees exposed to hazardous substances.
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A professionally designed LEV system helps:
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Protect employee health
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Improve workplace air quality
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Reduce dust build-up
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Improve productivity
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Reduce maintenance costs
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Increase energy efficiency
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Support COSHH compliance
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Improve overall workplace safety
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At A-Mac Environmental, every system is designed around your workplace, processes and operational requirements to ensure maximum performance.
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Maintaining an LEV System
Installing an LEV system is only the first step.
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To continue operating effectively, systems should be:
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Inspected regularly
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Maintained in accordance with manufacturer recommendations
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Kept clean
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Monitored for airflow performance
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Subject to a Thorough Examination and Test (TExT) at least every 14 months, unless more frequent testing is required.
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Regular maintenance helps ensure the system continues to protect employees and remains compliant with COSHH Regulations.
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Frequently Asked Questions
Is LEV better than general ventilation?
Yes. General ventilation dilutes contaminants within a building, whereas LEV captures hazardous substances directly at the source before they spread through the workplace.
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Can one LEV system serve multiple machines?
Yes. Many centralised LEV systems are designed to extract contaminants from multiple workstations simultaneously, provided they are correctly designed and balanced.
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Can an LEV system be upgraded?
Absolutely. Existing systems can often be improved by upgrading fans, filters, ductwork or extraction points to increase efficiency and meet changing production requirements.
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How do I know if my LEV system is working correctly?
The best way is through regular inspection, maintenance and a professional Thorough Examination and Test (TExT). Signs of poor performance can include visible dust or fumes escaping into the workplace, reduced airflow or unusual fan noise.
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Who should design an LEV system?
LEV systems should be designed by experienced specialists who understand airflow, contaminant control, COSHH requirements and HSE guidance. A correctly designed system is essential for effective long-term performance.
Whether you need a new LEV system, an upgrade to an existing installation or a Thorough Examination and Test (TExT), A-Mac Environmental can help.
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Our experienced engineers provide complete LEV design, installation, testing and maintenance services throughout Scotland, helping businesses create safer, cleaner and fully compliant workplaces.