What is LEV and why is it needed?

Local exhaust ventilation (LEV) is an air filtration system that has been specially engineered to remove harmful and hazardous substances from a working environment. The LEV system is specially designed to keep workers safe, removing the air pollutants and safely releasing them into the atmosphere, to comply with health and safety regulations.

Read on to find out how LEV systems work and, as a business owner, what your responsibilities are when it comes to inspecting and testing your LEV systems.

LEV: What do you need to know?

For those who install, maintain and provide LEV engineering systems, additional safety standards must be met to comply with the appropriate occupational health and safety requirements.

When there is the risk of harmful substances being exposed within a workplace, particular control measures must be considered. In instances where harmful substances cannot be removed or substituted, there is a hierarchy of actions that must be followed. LEV is simply one of the engineering control measures laid out by the Health and Safety Executive.

What is Local exhaust ventilation and What is it used for?

LEV is the common abbreviation for local exhaust ventilation, an essential engineering system that is often used to protect employees from hazardous substances in their workplace. A crucial part of occupational health and safety requirements, where hazardous substances cannot be removed from a business’s operations, additional safety measures are required. Therefore, when a local exhaust ventilation system is installed, it is paramount that the system has been meticulously designed and produced, properly installed and well maintained. When all these processes come together, the result is an effective system that keeps people safe.

The need for an LEV system cannot be stressed enough. When employees are exposed to these hazardous substances, such as dust, fumes or chemical vapours, it is extremely possible for them to suffer from adverse health problems. The severity of the impact will vary depending on the frequency of the exposure, as well as the duration and the degree. For example, carbon monoxide poisoning can take immediate effect, whereas asbestos exposure is known to have a long latency period. Therefore, business owners must ensure their risk assessments thoroughly investigate the potential exposure to any chemical and biological agents.

Employees who do end up suffering from occupational illnesses due to their substandard working conditions will have a legal case against your business. If your working environment does not have the appropriate control measures, you are putting your employees’ health at risk and your business at risk financially. LEV systems and other control measures are particularly important to specific industries, including:

  • Chemical Processing
  • Pharmaceutical Organisations
  • Biotechnology Companies
  • Bakeries
  • Woodwork
  • Welding
  • Paint-Spraying
  • Stonemasonry
  • Foundry Work
  • Certain Fields of Engineering

This list is not exhaustive, all businesses should investigate their own need for measures to reduce hazardous substance exposure. Fortunately, this comprehensive LEV guide will help you understand how local exhaust ventilation systems are able to extract the contaminants, preventing hazardous exposure.

An Overview of Local Exhaust Ventilation Systems

To keep it simple, local exhaust ventilation aims to contain and capture hazardous substances locally, at the emission point through an engineering system. It is important for employers to have a basic understanding of the workings of the LEV system to understand why certain particular maintenance actions are required.

For example, LEV contains specific design characteristics to help control hazardous substances from different sources. For certain contaminants alterations are required to ductwork, also fans may need alternative velocities. By understanding the basic components required within an LEV system, can help business owners understand the importance of the safety examinations that are needed.

The Five Elements of Local Exhaust Ventilation Systems

The LEV system is able to remove vapour, dust, mist and other airborne contaminants, it does this through five key components:

  • A Hood
  • Ducting
  • An Air Filter
  • A Fan
  • Discharge Point
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LEV Hoods

The hood is where the harmful contaminants enter the LEV system; therefore, it is crucial that they are designed and installed where they can be as effective as possible. To do so, the hood of the LEV system needs to be positioned as close to the source of the hazardous substances; the most successful systems will have a hood less than one diameter away.

Similarly, the LEV hood must have the ability to generate a sufficient airflow, enough to capture and draw in all the airborne contaminated substances. Likewise, it must be suitable for the type of contaminated substance; for example, does your workplace have a problem with dust or fumes? Having a consultation with an industrial ventilation engineer will be able to advise you on what hood is needed and what airflow you need.

In addition, having a hood that encloses the area in question, will help to avoid draughts blowing the contaminated air back into the workplace. These factors are paramount as you want to avoid any workers standing between the hood and the source of the hazardous substances.

There are two different types of hoods you can choose between for your LEV system, these are enclosing hoods and capturing hoods.

Enclosing Hoods

Enclosing hoods ensure contaminated air is contained and includes models such as the glove box and the spray booth. A glove box hood aims to both protect the employee and prevent the harmful particles from entering the wider workplace.

Whereas, a spray booth offers a separate enclosure where the operator can work and the contaminated air is contained. For employees to work within the spray booth, they must wear the appropriate PPE (personal protective equipment).

Capturing Hoods

Capturing hoods are the most common local exhaust ventilation hood that is used. They are designed so all work takes place outside of the hood, as well as the sourcing and containment of the hazardous substances. Models of capturing hoods include on-tool hoods, moveable capturing hoods, fixed, portable or flexible capturing hoods, and extracted workbenches.

To operate in this way, the LEV system has to generate sufficient airflow to draw in the contaminated particles. Moreover, workers must be located in a separate location to the contaminated air, or the captor hood must be located in between the two. If a business owner opts for this system, they must understand the maximum distance their workers must be away from the hood and the source of the contamination.


Ducting is a network of contained passages that are installed to safely transport the contaminated air to a filter. When considering what ductwork to install for easier maintenance, it is recommended to choose ducting that has no sharp corners. Ducting, instead, with flexibility is much less complicated to clean and maintain. Maintenance is paramount with ducting as dust build-ups have been known to collapse LEV systems, as the passages buckle under the weight; but, also, access dust can pose a fire risk if left unattended.

Air Filter

The LEV system’s air filter is also referred to as the cleaner or scrubber. It is at this point of the ventilation system where the contaminants are separated from the air. Similar to selecting the correct hood, some air filters are best suited for different contaminants. With expert advice, you can ensure your LEV system is best equipped for the job. Additionally, the filter will need regular cleaning without exposing the contaminants. Getting into good habits with the cleaning routine will ensure your LEV continues to work as efficiently as possible.


The fan within the LEV is the element that powers the system and moves the contaminated air along, through the ducting and towards the discharge point. The fan needs to be carefully positioned, this element must be accessible for cleaning and maintenance, but it can be a noise hazard for your employees. Moreover, when considering the size and type of fan, it is best to consult a professional industrial ventilation engineer.

Discharge Point

The discharge point, also known as an exhaust stack, is an exhaust that releases contaminated air into the atmosphere. When arranging for an LEV system to be implemented within your workplace, it is essential to identify a safe release point.

Often, this position is on an external wall or through the roof. It is important as well to release the contaminants into the air at a point one and a half times above the highest point of the roof. Also, consider the air is not discharged into a public space or close to an inlet for your or a neighbouring air conditioning system. Again, speak to a qualified engineer for advice, they can also help you ensure the discharge point can cope with the volume of air your system is removing.

The Importance of Good Design

As local exhaust ventilation systems are implemented to control harmful exposure to contaminants, the business owner must be on top of their risk assessment. In thoroughly assessing the hazards, the following must also be considered: your LEV system must be of good design and fit for purpose. By understanding all your potential hazards, your LEV system can be designed to meet your needs.

We have already touched upon these necessities, but let us go over them again. To ensure your LEV system is right for your workplace, the airflow rate must be sufficient for your system’s initial capture or containment. This includes its ability to carry all the air to the filtering system. If some contaminants are not removed in their entirety, this can pose a fire risk in the future, such as combustible wood dust.

A new consideration comes with the positioning of the ducting. The ductwork must be designed to avoid eddy currents and hindrances to the airflow. Not only are right-angled corners difficult for cleaning, but they also hinder the flow of contaminants; dead areas will be created and harmful substances can gather here.

Furthermore, the design should be leak-proof. Whether these leaks stem from the filter’s inefficiency to remove the contaminants, or the pressure within the ducting is too intense. Any risk of a leak can have considerable consequences.

Why Are LEV Systems Necessary?

Local exhaust ventilation is a crucial part of occupational health and safety where hazardous substances are released into the air. To mitigate the risk of your employees, or anyone visiting your premises, being affected as a result of your operations, the correct ventilation system must be implemented.

In 2021, there were 12,000 deaths from occupational lung disease in the UK and a further 17,000 estimated new cases of self-reported work-related pulmonary problems. And, this is with the current requirements specified within the Health and Safety At Work Act 1974.

Therefore, all employers must take action to prevent or adequately control exposures to contaminated substances, as outlined within Section 5, "General duty of persons in control of certain premises in relation to harmful emissions into the atmosphere." Installing an LEV system will help your business clean the air and protect your members of staff.

LEV Installation and Beyond

Once a business has identified its responsibility to implement an LEV system and designed the appropriate ventilation system for the premises, it is time to install the local exhaust ventilation. Before you go ahead with the implementation, it is worth contacting your local council to ensure if you require a building consent first.

While your LEV system will most likely have been designed by a competent and qualified professional, it is worth consulting an occupational hygienist to ensure your needs are definitely met. When everything has been checked, signed off and installed, there are some additional steps to follow to guarantee the effectiveness of the system.


The next step in the process is to get the local exhaust ventilation commissioned. By commissioning the system, it is proven to be working correctly and the chosen LEV is the suitable type and size to protect your workers. The report that is produced will provide the point of reference for all future tests, consequently, a copy of the commission will remain with the ventilation system until it is removed.

Maintenance and Servicing

To continue to comply with the Health and Safety Executive’s regulations, the LEV system must be regularly maintained and services as outlined by the manufacturer. Records of such checks must be logged within the user manual, noting down all daily, weekly and monthly performance reviews, as well as the system’s overall condition. Such checks should include:

  • Assessing the hood for physical damage and blockages, as well as checking airflow indicators.
  • Examining the ducts for wear and tear, partial blockages and any damage.
  • Verifying the position of dampers.
  • Assessing the filters for any damage, pressure across the clear or if any failure alarms have been triggered.
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Training and Testing

Ensuring all staff receive thorough training on how to use the LEV system is critical. They must know how to identify any issues that would interfere with its correct operation, any limitations the implemented system may have and how they must incorporate the ventilation within their day-to-day workings.

Once the staff are all trained, the system must undergo statutory examinations by a competent person every 14 months. These official inspections offer a detailed and systemic evaluation of the ventilation system, ensuring they are performing as intended and provide adequate protection and control of the hazardous substances. The results of each inspection must be kept on record for at least five years.

The Legal Obligation of LEV Inspections

Local exhaust ventilation regulations state that the local exhaust ventilation system must undergo official inspections, this will assure Health and Safety that the system is in good working order. LEV inspections, however, are also legally required under Regulation 9 of the Control of Substance Hazardous to Health (COSHH) 2002. The use of nano-materials is regulated to control the risk imposed by these substances, and inspecting LEV systems is the most efficient way to ensure a company’s measures remain up to standard.

Every 14 months, LEV must undergo this statutory requirement; but, for some businesses their systems will need to be assessed every 6 months. This ruling is applicable for premises that grind, abrade or polish metal for more than 12 hours a week. Moreover, if shot-blasting is carried out or metal castings are cleaned, inspections are legally required monthly.

An effective inspection is completed in 3 stages:

  1. A Visual Examination – a thorough inspection to ensure everything is in working order.
  2. Technical Checks – to measure and investigate the performance of the LEV technically, inspecting the conformity with the initial commission.
  3. Check Exposure – an assessment to ensure the exposure levels are safe for workers.

Once an inspection has been completed it is vital that you retain the detailed reports the examination collates.

Spiers LEV Testing

At Spiers, our P601 qualified engineers can take care of your LEV testing for you. After a thorough examination, we will even provide you with detailed records using our custom-made software solution, RiskMach. Working nationwide, you can get your annual LEV testing inspection booked in with our Safety Engineer. Get in touch today.

Frequently Asked Questions

Is LEV a legal requirement?

Yes, the installation of a local exhaust ventilation system is legally required under Section 5 of the Health and Safety At Work Act 1974. Further upkeep and maintenance is also a legal requirement under Regulation 9 of the Control of Substance Hazardous to Health (COSHH) 2002.

How does exhaust ventilation work?

LEV systems work by capturing or containing the air pollutants within a large hood, using a network of ducting to draw this air towards an industrial filter. Here the hazardous substances are captured and separated from the air, being released high above the premises through a discharge point, also referred to as an exhaust. Some LEV systems require workers to use PPE when working within a contained hood; however, others aim to intercept the particles before they reach the worker’s designated area.

How do local exhaust ventilation and general ventilation differ?

The main difference between LEV systems and general (dilution) ventilation systems is how they aim to reduce the risk associated with air pollutants. Local exhaust systems are much more efficient, capturing or containing harmful substances and removing them from the air in the workplace. Whereas, general ventilation systems opt to dilute the concentration of the pollutants by drawing in clean air from outside and mixing the two together.