An LEV system may perform correctly when commissioned or thoroughly tested, but its performance can change between formal examinations. Filters can become loaded, ducts partially blocked, dampers moved, and components damaged or worn.
LEV performance monitoring helps operators identify these changes earlier. Airflow indicators and other suitable monitoring methods can show whether relevant system parameters remain within their expected operating range.
For employers in Northern Ireland, performance monitoring should form part of a wider approach to checking, maintaining and testing LEV under the Control of Substances Hazardous to Health Regulations (Northern Ireland) 2003.
LEV performance monitoring involves checking appropriate system parameters to identify whether local exhaust ventilation continues to operate as expected.
This may involve a simple, continuously visible airflow indicator or a more sophisticated device that alarms when airflow or another monitored parameter moves outside a predetermined range.
The HSE's LEV guidance explains that employers should make sure their LEV has airflow indicators, or an equivalent means of checking performance, and that systems are regularly checked and maintained.
Performance monitoring complements routine maintenance and competent Thorough Examination and Testing (TExT). It does not replace them.
LEV is used to capture or contain airborne contaminants such as dust, mist, fumes, gases and vapours close to where they are generated. For that control to remain effective, the system needs to continue operating within its established performance parameters.
A running fan does not necessarily demonstrate that sufficient airflow is reaching every extraction point. Similarly, an operator cannot reliably assess air velocity at a hood simply by putting a hand near it.
The HSE explains in its LEV airflow guidance that a suitable airflow indicator can make it easier to see whether airflow remains adequate.
The Health and Safety Executive for Northern Ireland (HSENI) also recommends routine checks covering components such as:
The appropriate frequency and type of routine check will depend on the system, process and manufacturer's or competent person's recommendations.
An airflow indicator helps operators see whether a relevant LEV performance parameter remains within its expected range.
One relatively simple example is a manometer. Depending on the system design, pressure can be used as an indicator of whether expected airflow conditions are being maintained.
More sophisticated devices may provide an alarm when airflow drops below a predetermined trigger level.
The appropriate indicator depends on factors including the LEV design, the parameter being measured and the potential health risk. HSE notes that a simple indicator may be appropriate for a lower-risk situation, while more hazardous circumstances may justify a more sophisticated device.
Importantly, the indicator needs to show clearly whether airflow is adequate.
Where a system does not currently provide operators with a practical way of seeing this, suitable airflow indicator installation can make performance information more visible during normal operation.
LEV performance can change because of:
A build-up of material, for example, could restrict airflow, while damaged ductwork could affect how the system performs.
An indicator moving outside its established operating range can alert operators to a potential problem, but it will not necessarily identify the cause. Further investigation may therefore be required.
Performance monitoring is most useful when there is a meaningful benchmark.
Commissioning provides an opportunity to establish satisfactory performance benchmarks while the LEV is operating as intended.
HSE's LEV commissioning guidance explains that commissioning should establish performance standards that can subsequently be used as references for examination, maintenance and performance management.
Depending on the system, relevant information might include airflow, pressure or other technical measurements. These benchmarks can then help determine the appropriate operating range for an indicator.
This is one reason commissioning and ongoing testing perform different but connected roles in LEV management.
Where systems have been modified, or their original commissioning information is unavailable, competent assessment may be needed to establish appropriate performance criteria.
An abnormal airflow indicator reading means that the monitored parameter is no longer where it is expected to be. It does not automatically tell you why.
Possible causes could include a blocked filter, damaged ductwork, an altered damper, a fan problem or another change affecting system performance.
The response should follow the LEV user manual and workplace procedures. Depending on the system, this may involve checking the hood, ductwork, filters, dampers, fan and indicator, as well as any recent changes to the process.
If the cause cannot be identified or there is uncertainty about whether exposure remains adequately controlled, competent LEV or occupational hygiene advice may be required.
Not by itself.
An airflow indicator provides information about a particular system parameter. A reading within the expected range can indicate that this aspect of performance remains consistent with the established benchmark, but it does not prove that every part of the LEV is performing correctly or that employee exposure is adequately controlled.
Effective control can also depend on hood design and position, contaminant behaviour, operator technique and the condition of other system components. In some workplaces, occupational exposure monitoring may also be appropriate.
LEV performance monitoring should therefore be treated as one part of a wider control strategy.
The value of an airflow indicator depends partly on whether operators understand it.
Workers using LEV should know:
HSE's guidance for employees using LEV recommends checking the system each time it is used, including the indicator and signs such as unusual noise, vibration, smells or settled dust.
Training can help operators understand both what an indicator shows and its limitations.
LEV performance monitoring and Thorough Examination and Testing serve different purposes.
Monitoring helps operators recognise changes during everyday operation. A TExT provides a more detailed and systematic assessment of the system's condition and performance.
For businesses in Northern Ireland, HSENI states that most LEV equipment must be thoroughly examined and tested by a competent person at least every 14 months. Some processes have shorter maximum intervals, and more frequent testing may be appropriate where system effectiveness could deteriorate between tests.
A competent LEV testing programme therefore remains necessary even where airflow indicators are fitted.
For a more detailed explanation of what happens during testing and how it differs from everyday monitoring, see LEV Testing Explained: Legal Requirements for UK Businesses.
LEV performance monitoring should complement TExT, not replace it.
A change in an indicator reading is useful only if there is a process for responding to it. Planned LEV maintenance may include cleaning, filter replacement, component inspections, repairs and checks or calibration of monitoring equipment.
Maintenance intervals should reflect the particular system, how it is used, manufacturer's information and competent advice rather than assuming the same schedule applies to every LEV system.
Monitoring should also leave a useful record. HSENI advises that user checks, maintenance and servicing should be recorded in the LEV system's logbook.
Useful records may include:
Maintaining an LEV logbook can make it easier to see what has happened to the system over time and identify recurring issues.
Records can also provide useful context when the system is next examined or maintained.
Formal TExT documentation serves a different purpose from routine monitoring records. Our guide to COSHH Risk Assessment and LEV Compliance explains how LEV forms part of the wider approach to controlling exposure and meeting COSHH duties.
There is no single monitoring approach suitable for every LEV system. The approach should reflect the system design, hazardous substance, process, potential exposure risk and the parameters that demonstrate satisfactory performance.
In practice, this may combine operator checks, suitable airflow or performance indicators, commissioning benchmarks, planned maintenance and periodic Thorough Examination and Testing. Where appropriate, separate occupational exposure monitoring may also be required.
These measures perform different functions but work together as part of effective LEV management.
An airflow indicator or equivalent monitoring method can help show whether relevant system parameters remain within their expected range. Operators should also look for physical damage, unusual noise, vibration, settled dust and other changes. Routine checks do not replace maintenance or Thorough Examination and Testing.
There is no specific legal requirement for an airflow indicator on every individual LEV hood. However, HSE states that employers need a way to check that adequate airflow is being maintained and recommends airflow indicators or suitable equivalents. The appropriate monitoring arrangement depends on the system and risk.
It depends on the system and potential health risk. A simple manometer may be suitable in some applications, while higher-risk situations may require a more sophisticated indicator or alarm. The indicator should clearly show whether the relevant airflow condition is adequate.
Not necessarily. HSE notes that different monitoring approaches may be suitable for different systems. For example, measuring static pressure across a filter may provide a useful indication for some simple LEV arrangements. The monitoring method should be selected according to the system design and performance requirements.
No. An airflow indicator can help identify changes in system performance during everyday use, but it does not replace statutory Thorough Examination and Testing. In Northern Ireland, most LEV equipment must be thoroughly examined and tested by a competent person at least every 14 months. Some processes have shorter maximum intervals, and more frequent testing may be appropriate depending on the system and its condition.
Follow the system's user manual and workplace procedures. A low or abnormal reading may indicate a filter, duct, damper, fan or other system issue. If the cause cannot be established or there is uncertainty about control effectiveness, the system should be assessed by someone with appropriate competence.
LEV performance should not simply be assumed between formal examinations. Suitable airflow indicators and routine checks can help operators recognise changes earlier and identify when further investigation may be needed.
Effective LEV performance monitoring works alongside commissioning, operator training, planned maintenance, record-keeping and competent Thorough Examination and Testing.
If your existing LEV does not provide a clear way for operators to recognise changes in airflow, DevineAir can assess the system and advise on suitable airflow indicators and performance parameters.
This article provides general information about LEV performance monitoring. Appropriate monitoring, maintenance and testing arrangements depend on the individual system, process and hazardous substances involved. Site-specific COSHH assessment and competent advice may be required.
LEV commissioning and LEV testing both assess local exhaust ventilation performance, but they serve different purposes. Commissioning establishes how an LEV system should perform when it is brought into use, while Thorough Examination and Testing (TExT) assesses its ongoing condition and performance. Understanding LEV commissioning vs testing is particularly important when a new system is […]
Health and Safety Executive (HSE) inspections can take place in any workplace where employees may be exposed to hazardous substances. During these inspections, businesses are expected to demonstrate that suitable measures are in place to control exposure to dust, fumes, vapours, and other airborne contaminants. Need expert help? DevineAir provides LEV logbooks for employers across […]