Every workplace that handles hazardous substances has a legal duty to protect employees from exposure. Airborne contaminants such as dust, fumes, vapours, and mists can pose serious health risks if they are not effectively controlled.
A risk assessment under COSHH can help employers recognize such dangers and find out what the best controls for those risks would be. Where there are contaminants that become air borne, Local Exhaust Ventilation (LEV) may be the best form of engineering control.
However, installing an LEV system is only part of the process. This guide explains how a COSHH risk assessment LEV approach helps businesses comply with UK legislation, protect employees, and maintain effective workplace controls.
COSHH Risk Assessment helps to identify any dangerous substances within the workplace and the methods that can be used to limit exposure among the employees. If the control method used does not provide a sufficient level of control for any airborne contamination, it may be necessary to use Local Exhaust Ventilation (LEV). It is also important for employers to ensure that the LEV system has been designed, tested and Thoroughly Examined and Tested (TExT).
The Control of Substances Hazardous to Health (COSHH) Regulations 2002 require employers to assess and control the risks associated with hazardous substances used or generated in the course of work.
A COSHH risk assessment is not simply a paperwork exercise. It is a practical process that helps businesses understand where harmful exposure could occur and what steps are needed to prevent it.
A typical assessment considers:
Hazardous substances covered by COSHH include:
The Health and Safety Executive (HSE) provides comprehensive guidance on COSHH and employers' responsibilities, helping businesses understand how to assess and manage these workplace risks.
Once a COSHH assessment identifies airborne contaminants, employers must determine the most effective way to control exposure.
The COSHH hierarchy of control prioritises eliminating the hazard. If that is not reasonably practicable, employers should consider substituting safer materials or introducing engineering controls before relying on personal protective equipment (PPE).
LEV sits high in this hierarchy because it removes contaminants before workers inhale them. Instead of allowing hazardous substances to spread throughout the workplace, an LEV system captures them directly at the source and safely extracts or filters them.
Examples of LEV systems include:
For many industrial processes, LEV is not simply good practice. It is often the most appropriate engineering control identified during a COSHH risk assessment.
Not every workplace requires Local Exhaust Ventilation, but many industries generate airborne contaminants that cannot be adequately controlled through general ventilation alone.
Your COSHH assessment may identify the need for LEV where work activities produce:
For example, a fabrication workshop carrying out daily welding operations will generate hazardous welding fumes. During the COSHH assessment, these fumes may be identified as a significant health risk. Installing extraction arms near each welding station captures fumes before they enter employees' breathing zones, significantly reducing exposure.
Similarly, a woodworking manufacturer producing hardwood furniture may require dust extraction systems to control fine wood dust, which is recognised as a hazardous substance under COSHH.
Laboratories provide another example. Fume cupboards and microbiological safety cabinets help protect both laboratory staff and sensitive processes by safely containing hazardous substances generated during testing and research.
One of the most common misconceptions is that installing an extraction system automatically satisfies COSHH requirements.
In reality, employers remain responsible for ensuring that the system continues to perform effectively throughout its operational life.
An LEV system should be:
The HSE's HSG258: Controlling Airborne Contaminants at Work is widely recognised as the leading guidance document for the design, commissioning, maintenance, and testing of LEV systems. While HSG258 is guidance rather than legislation, following its recommendations helps businesses demonstrate that their extraction systems meet the expectations of the COSHH Regulations.
Consultation with knowledgeable LEV specialists in the design phase is useful in ensuring proper specification of the system. At DevineAir, we offer services such as LEV design and consultancy which assist businesses to have engineering controls in place for COSHH compliance.
A COSHH risk assessment should be reviewed whenever new equipment, substances, or work processes are introduced. If LEV is used as a control measure, the assessment should also confirm that the system continues to provide adequate protection.
A practical approach involves the following steps:
Start by listing out all the harmful materials that may be present or produced during the course of work activities. This would not only include the chemical materials that may have been brought in from outside the workplace but also those produced in the course of manufacturing processes.
Safety Data Sheets (SDS), manufacturer information, and HSE guidance are useful sources of information when assessing potential hazards.
Consider everyone who could come into contact with hazardous substances. This may include machine operators, laboratory staff, maintenance engineers, cleaners, contractors, and even nearby visitors.
Knowing the route of exposure will help to ascertain whether any extra precautions are necessary.
Identify existing controls that have been established. In case there are any airborne contaminants, then consider whether the LEV is effectively capturing them at the source level or they are escaping into the workplace.
Though general ventilation could help to increase airflow, it does not necessarily mean that it will control hazardous substances where source extraction is necessary.
The LEV system must be tailored to match the particular process to be controlled. The hood design, the air flow, ducting design, filters used and the fans are some of the factors that influence the effectiveness of the contaminant capture.
Where there have been changes in the manufacturing process or machinery installed, the existing exhaust system may not fit. This means that it would be prudent to seek review of the system by qualified professionals.
Documentation of assessment should be done, action needs to be taken and a schedule for review needs to be set. Risk assessments in COSHH need to be reviewed and updated in case of substantial change in substances, equipment, practices, and layout in the workplace.
This will ensure effectiveness of control measures.
Even the best-designed LEV system can become ineffective if it is inspected or maintained incorrectly.
The HSE expects employers to ensure that anyone responsible for designing, examining, testing, or maintaining an LEV system is competent. Competence combines appropriate training, practical experience, technical knowledge, and an understanding of current guidance such as HSG258.
Working with qualified occupational hygiene professionals gives businesses confidence that their systems are being assessed against recognised industry standards.
According to the COSHH regulation 9, it is important for the employers to ensure that LEV systems work efficiently, stay in good repair and remain clean.
In general, this involves carrying out the Thorough Examination and Test (TExT) within 14 months. Nevertheless, some industries have different requirements regarding the frequency of testing depending on the nature of work done there.
A Thorough Examination and Test typically includes:
These examinations provide evidence that the system continues to control exposure effectively while highlighting any maintenance or corrective work required.
DevineAir's LEV Testing service provides detailed reports and practical recommendations, helping businesses demonstrate compliance while maintaining safe working environments.
Compliance is not achieved through testing alone.
Over time, filters can become blocked, ductwork can develop leaks, extraction hoods may be repositioned, and mechanical components naturally wear out. These changes can significantly reduce extraction performance without being immediately obvious.
Routine LEV Maintenance helps identify these issues before they affect employee safety or lead to equipment failure.
Preventive maintenance can:
Recording information regarding maintenance also assists in proving proper management of the system in the time between inspections.
The purpose of a COSHH Risk Assessment LEV approach is not simply to fulfill legal requirements but to offer an organized method for recognizing hazards, assessing exposure risks at work, and using effective engineering controls to protect workers on a daily basis.
The use of well-designed extraction systems along with maintenance, inspection, and thorough testing makes LEV one of the most effective means of reducing exposure to toxic substances.
At DevineAir, we provide end-to-end support for businesses across the UK, including LEV Design, LEV Consultancy, LEV Testing, LEV Maintenance, LEV Awareness Training, Fume Cupboard Testing, Microbiological Safety Cabinet (MSC) Testing, and a full range of occupational hygiene services. Our experienced team works with organisations across multiple industries to help create safer, healthier, and fully compliant workplaces.
Whatever you may need in terms of COSHH risk assessments, an assessment for the installation of a new LEV system, or even the scheduling of your next Thorough Examination and Test, we’re here to help. We can work with you to make sure that your LEV system is still as efficient as ever.
Not in every workplace. A COSHH risk assessment determines whether Local Exhaust Ventilation is necessary. If other measures cannot adequately control hazardous airborne contaminants, LEV is often the most appropriate engineering control.
Most LEV systems must undergo a Thorough Examination and Test at least every 14 months under COSHH. Certain industries and specialist systems may require more frequent examinations.
HSG258, Controlling Airborne Contaminants at Work, is the HSE's recognised guidance document for the design, commissioning, maintenance, and testing of LEV systems. Following its recommendations helps businesses demonstrate good practice and support compliance with COSHH.
Competent professionals with the appropriate training, knowledge, and practical experience should complete LEV testing. Using qualified specialists helps ensure accurate testing, reliable reporting, and confidence in your system's performance.
No. The need for LEV depends on the hazardous substances involved and the level of exposure identified during the risk assessment. Some workplaces may be able to control risks through elimination, substitution, or other engineering controls, while others require LEV to protect employees effectively.
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