Before the visit
Give the examiner the commissioning report, user manual, system logbook and previous thorough examination and test report where they are available. Tell them about changes to the process, layout or LEV since the last visit. Relevant air sampling records and details of how operators use the system can also help them assess whether control remains effective.
Arrange safe access to hoods, ducts, filters, fans and marked test points. The examiner needs to see the normal process and contaminant source, so plan for the equipment and extraction to run under representative operating conditions. Explain site hazards, permits, isolation procedures and protective equipment before work starts. Remove avoidable obstructions, but do not hide faults or change settings simply to improve the reading.
The three stages
HSG258 divides a thorough examination and test into three stages. Stage 1 is a thorough visual and structural examination. The examiner checks that the LEV is in efficient working order, in good repair and clean. This can include external damage, internal duct condition, filters, cleaning devices, alarms, the fan drive and signs of dust escaping around a hood.
Stage 2 reviews technical performance against commissioning data or another suitable source. Stage 3 assesses control effectiveness. The examiner brings together what they saw, the measurements, challenge tests and the way operators use the LEV. The final judgement is whether the system can continue to perform as intended and contribute to adequate control of exposure.
What the examiner measures
Measurements depend on the design. They may include air velocity at a hood face, velocity in branch and main ducts, static pressure at marked points, pressure across a filter and fan performance. The examiner can calculate volume flow from the measurements and compare results with the commissioning report, user manual or another recognised performance standard.
Smoke can show whether a hood captures the contaminant cloud or lets it move into a worker's breathing zone. A dust lamp can make escaping dust or mist visible while the process runs. The examiner may also check alarms, fan direction and speed, make-up air, filter performance and relevant air sampling. Not every method suits every system, so the report should state what was used.
How long the visit takes
There is no fixed time for an LEV test. The examiner has to identify and inspect the system, observe the process, reach the test points, take repeatable measurements and assess each hood. A small single-hood system is a different job from a multi-branch system serving several processes, filters and discharge points.
Ask the examiner what access and production time they need when requesting a quote. Give an accurate count of systems and hoods, and mention restricted access, permits or processes that take time to start. Do not choose a service only because it promises the shortest visit. The test must be detailed and systematic enough to support the result in the written report.
What pass or fail means
A satisfactory result means the evidence supports that the LEV can perform as intended and contribute to adequate exposure control under the conditions tested. An unsatisfactory result means the examiner found defects or performance problems that prevent that conclusion. The report should explain the faults, prioritise the actions and state what needs repair, adjustment or further assessment.
HSG258 gives four criteria for a red failed label: reduced or no detectable airflow; an enclosing hood failing to contain the contaminant cloud; a receiving hood failing to intercept or contain it; and a capturing hood failing, for example because its capture zone does not encompass the working zone. A label is not mandatory, but warns operators directly. The examiner should promptly report critical defects to the employer.
After the visit
You should receive a written report that identifies the LEV and operating conditions, records its condition and measurements, compares performance with the intended standard and gives a clear result. It should include any repairs or adjustments made during the visit, any critical defects and a prioritised plan for further action. Read it and ask the examiner to explain anything unclear.
Where labels are used, each hood or the system should show the test date, the next test date and the examiner. Keep the report for at least five years and place the next due date in your maintenance plan. Complete the actions by their stated priorities, record repairs and arrange a competent check or retest where needed to confirm control has been restored.
Questions duty holders ask
Does production need to run during an LEV test?
Usually, yes. The examiner needs representative operating conditions to observe the contaminant source and assess capture. Agree the exact arrangements and safety controls before the visit.
Will the examiner open the ductwork?
Stage 1 can include internal duct examination where appropriate. Safe access, isolation and the system design determine what can be inspected.
How long does an LEV test take?
There is no standard duration. It depends on the number of systems and hoods, their complexity, access, process conditions and the measurements required.
What happens when an LEV system fails?
The examiner should explain the defect and prioritise remedial work. Unsafe work should not continue without effective control, and a competent person should confirm control after repairs.
Is your next test due?
Put in the date of the last test and get the deadline, with a reminder if you want one.
LEV test due date calculatorUse the directory to find an LEV tester near you.
Sources
- HSE: LEV frequently asked questions, opened 23 September 2026
- HSE: Controlling airborne contaminants at work, HSG258, opened 23 September 2026
- HSE: HSG258 full guidance, opened 23 September 2026