Local exhaust ventilation (LEV): what employers must inspect, test and maintain

Start with the COSHH assessment, not the extractor catalogue

Under the Control of Substances Hazardous to Health Regulations 2002, employers must assess exposure and prevent it where reasonably practicable. Where prevention is not reasonably practicable, exposure must be adequately controlled. LEV may be part of that solution, but buying extraction does not remove the need to understand the contaminant, process, people exposed and level of control required.

Identify what the work releases, how and where it becomes airborne, the quantity and frequency, relevant workplace exposure limits and who may be affected. Typical examples include welding fume, wood or stone dust, paint mist, flour dust, solder fume and metalworking-fluid mist. A fabricator on Teesside and a small joinery in County Durham may both need extraction, but the hood, airflow and operating method will not be interchangeable.

Apply the control hierarchy first. Eliminate or substitute the hazardous material or process where reasonably practicable, then consider enclosure and engineering control. LEV should capture contaminant before it reaches the breathing zone. General ventilation or an open workshop door is rarely a substitute for effective source capture where LEV is needed.

Related guide: a safety data sheet is not a COSHH assessment → · HSE: introduction to LEV ↗

Commission new or materially changed LEV before relying on it

HSE says employers should commission LEV to establish that it adequately protects people from day one. Commissioning is more than switching on the fan. It should identify the contaminant and process, assess capture under real operating conditions, confirm the system is balanced and record performance benchmarks for later checks and statutory examinations.

A useful commissioning report identifies the system and hoods, describes the process and operating conditions, records the test methods and results, includes a simple schematic and gives measurable benchmarks such as flow rates, pressures or velocities. It should also cover filters, discharge, make-up air and any factors that influence performance.

Keep the commissioning information for the life of the system. If no reliable baseline exists, a competent LEV specialist may need to establish intended performance. A later examiner cannot meaningfully confirm that a complex system still performs as designed if nobody can say what that design performance was.

HSE: commissioning an LEV system ↗

Check performance during normal work—not only on test day

COSHH regulation 9 requires control measures to be maintained in an efficient state, efficient working order and good repair. The employer therefore needs routine checks between formal examinations. Operators should know how to position the hood, recognise normal indication or performance, report damage and stop or escalate work when control is doubtful.

A quick visual check can find a blocked hood, split flexible duct, damaged enclosure, full collector, unusual noise or altered process. Airflow indicators can give immediate warning when flow has fallen. HSE recommends them, although there is no universal legal requirement to fit one to every hood. The indicator must show something meaningful against an established adequate-performance range; movement of a paper tell-tale or feeling suction by hand is not reliable proof.

Record checks at a frequency based on risk, likelihood of deterioration and the manufacturer's or supplier's instructions. A high-use extraction arm exposed to impacts and repositioning may need more attention than a protected fixed enclosure. Supervisors should also observe whether workers can and do use the hood in the position assumed by the assessment.

HSE: LEV airflow and examination FAQs ↗

Separate maintenance from the statutory thorough examination and test

Servicing, filter changes and repairs keep the system working. A thorough examination and test—often shortened to TExT—is a detailed, systematic assessment of whether it can continue to perform as intended and contribute to adequate exposure control. One does not automatically replace the other.

COSHH requires LEV plant to be thoroughly examined and tested at least once every 14 months. That is a maximum interval, not a default promise that every system remains adequate for 14 months. Schedule 4 sets shorter intervals for certain processes: one month for specified blasting used in cleaning metal castings and jute manufacture, and six months for specified non-ferrous metal casting and mechanically powered grinding, abrading or polishing carried out for more than 12 hours a week. Risk, deterioration or specialist advice may justify more frequent examination in other cases.

Use a competent examiner with the knowledge, skills and experience relevant to the system. Ask what information they need, what tests will be completed and how the report will decide whether control is adequate. HSE does not prescribe one qualification as the only route to competence; a course certificate alone does not demonstrate the necessary practical capability.

COSHH regulation 9: maintenance, examination and test ↗ · COSHH Schedule 4: shorter LEV examination intervals ↗

Read the report and close defects

The employer retains the duty even when a specialist carries out the examination. The report should identify the system, intended performance, condition, test methods, measurements, conclusion and defects or remedial actions. Keep the examination-and-test record, or a suitable summary, for at least five years. Repairs resulting from it must also be recorded.

Do not reduce the process to a green label and a next-test date. Compare the findings with the commissioning baseline and COSHH assessment. Assign each action to an owner and date, restrict or stop affected work where control is inadequate, and arrange competent repair and confirmation of effectiveness before ordinary use resumes. HSE recommends clear failed-system labelling, supported by an immediate written explanation and remedial actions.

If a report cannot conclude that exposure is adequately controlled, the answer may involve hood redesign, process enclosure, changed working position or exposure monitoring—not just a larger fan. Review the COSHH assessment whenever the process, material, layout, hood or production rate changes, after control failure, or where health surveillance or exposure evidence raises concern.

Related guide: PUWER inspection requirements →

Account for connected risks and people

LEV can introduce additional hazards. Combustible dusts or flammable vapours may require a DSEAR assessment, suitable equipment, safe collection and discharge arrangements. Fans, ducting and filters can create noise, fire, manual-handling, work-at-height and maintenance risks. Recirculating filtered air demands particular care because failed filtration can return contaminant to the workplace.

Provide suitable information, instruction and training to operators, supervisors and maintainers. Explain what the system controls, correct hood position, normal indicators, user checks, limitations and defect action. Consider people who may be more susceptible to respiratory harm and whether health surveillance is appropriate for the substance and work. RPE may still be required for residual risk or exceptional tasks, but it should not conceal ineffective source control.

HSE: controlling airborne contaminants with LEV (HSG258) ↗

LEV employer checklist

The simplest management test is this: can the operator show what good performance looks like today, and can the manager show what will happen when it is not achieved? If the only answer is a test sticker, the control system is incomplete.

• Link every system and hood to a current, task-specific COSHH assessment.
• Confirm the LEV was commissioned and retain its performance baseline.
• Give each system and hood clear identification.
• Set operator checks and maintenance frequencies from risk and instructions.
• Provide a meaningful way to recognise adequate airflow or performance.
• Train workers in hood position, limits, checks and defect reporting.
• Schedule competent thorough examination and test within the correct interval.
• Keep examination, test and resulting repair records for at least five years.
• Stop, restrict or change work when extraction cannot adequately control exposure.
• Review the COSHH assessment after changes, failures or adverse evidence.