What is LEV testing?

What LEV is

Local exhaust ventilation (LEV) removes contaminated air at or near the point where a work process creates it. That may be dust from sanding, fume from welding or vapour from a solvent process. Capturing the contaminant close to its source helps stop it spreading into the air people breathe.

Most systems have a hood or enclosure at the process, ducting that carries the air, a fan that moves it and a filter or other air cleaner. The cleaned air then reaches a safe discharge point. These parts must work together. A damaged hood, blocked duct or failing fan can reduce control even when the system still sounds as though it is running.

HSG258 describes enclosing, receiving and capturing hoods. A fume cupboard is a partial enclosure; a downdraught bench is an example of a capturing hood. The choice depends on the process and the contaminant source. The examiner needs to understand that design when assessing the LEV system.

What the test is

A thorough examination and test, often shortened to TExT, is more than a quick service check. HSG258 describes three stages. The examiner first checks the system visually and structurally for damage, wear, cleanliness and working indicators or alarms.

They then review technical performance. Depending on the system, this can include airflow velocity and static pressure measurements, smoke or dust lamp checks and tests of the fan, filter and alarms. The readings are compared with the commissioning report, user manual or another suitable benchmark for the system's intended performance.

Finally, the examiner assesses whether the LEV is still controlling exposure as intended. The written report should state the result, explain any faults and set out the work needed to correct them. This gives the employer a record to read and act on, rather than a pass sticker without supporting detail.

How the test is carried out

HSG258 paragraph 337 states: "LEV examiners must have the appropriate equipment such as Pitot tubes, a smoke generator, a dust lamp, an anemometer and, sometimes, equipment for air sampling." The examiner selects methods suited to the installation. A smoke test helps show where air moves and whether contaminant can escape from the hoods. Filters, ducts and the fan also need checks appropriate to their design and condition.

For checks with the work process running, paragraph 106 names an anemometer, dust lamp or smoke tracer. It describes an airflow indicator as probably the simplest way to check that a hood is working properly. These user checks support ongoing control; they do not replace the statutory examination.

The measurements have different meanings. Face velocity is the average air speed across the open face of a hood. Capture velocity is the speed needed around the source to draw the contaminant cloud into the hood. Transport velocity concerns movement through the duct. Static pressure is the pressure difference between the inside and outside, measured with equipment such as a manometer. The examiner compares performance with commissioning information or other suitable standards rather than applying one reading to every installation.

Who must arrange a test

Regulation 9 of the Control of Substances Hazardous to Health Regulations 2002 (COSHH) covers maintenance, examination and testing of control measures. It requires employers to arrange a thorough examination and test of LEV at least once every 14 months, or at the shorter interval in Schedule 4 for the processes listed there.

In practical terms, the employer is the duty holder. They must arrange the test and act on the findings. Give the examiner the available commissioning information, user manual, logbook and previous report.

For on-tool extraction, HSE says the extraction unit itself needs testing. The interchangeable hoods and hoses need regular visual checks.

How often LEV testing is needed

HSE says most LEV systems should have a thorough examination and test at least every 14 months. Testing may need to be more frequent where wear could cause performance to fall between visits. A test label can show the last test and next due dates, but the label is not the legal record and there is no specific requirement to fit one.

The employer must keep the examination and test record, or a suitable summary, available for at least five years from the date it was made. Keep it with the system logbook, commissioning information and maintenance records so the next examiner can compare current readings with the intended performance. Use the LevHQ LEV test due date calculator for systems on the general 14-month interval.

Who can carry out the test

The examination must be carried out by a competent person. HSE defines competence as knowledge, skills and application experience together. A course certificate on its own does not prove competence, so ask about qualifications, practical experience and work on systems like yours. The examiner should also be able to explain what information they need and what the results mean.

The BOHS modules distinguish P600 Methods for Testing the Performance of Local Exhaust Ventilation Systems, P601 Thorough Examination and Testing of Local Exhaust Ventilation Systems, P602 Basic Design Principles of Local Exhaust Ventilation Systems, and P604 Performance Evaluation, Commissioning and Management of Local Exhaust Ventilation Systems.

These cover methods, examination, design and commissioning or management respectively. Ask which work the examiner is qualified and experienced to do. LevHQ lists qualifications claimed by each company, but does not verify them. Check evidence directly before appointing anyone.

What you should receive

You should receive a written report that identifies the system, records the examination and measurements, compares performance with the available benchmark and gives a clear result. Where performance is not as intended, the report should explain what is wrong and what needs to be corrected. Read it, ask about anything unclear and act on the recommendations.

The ILEVE TExT report template is currently version 1.5. Its twelve sections cover the executive summary, client and site details, plant and engineer information, conclusions, a schematic, photographs, the technical assessment and calibration certificates. ILEVE says using the template does not ensure compliance with the COSHH Regulations or HSE requirements. It does not ensure competence either.

You may also receive a test label for the system or each hood. HSE recommends labels as a clear way to show test status, but they do not replace the report. The related guide, Understanding your LEV report, explains how to read the findings and priorities.