What LEV Testing Does and When Further Assessment May Be Needed

Local exhaust ventilation (LEV) plays a critical role in controlling airborne contaminants in many workplaces. As a result, LEV testing is a common legal and practical requirement under COSHH and is frequently referenced following inspections or professional reviews.

LEV testing is an important part of exposure control — and in many cases, it is essential. However, while LEV testing confirms that a control system is functioning as intended, it does not, on its own, demonstrate whether worker exposure is adequately controlled.

This article explains what LEV testing is designed to do, why it is legally required, where its limitations lie, and how it fits most effectively within broader occupational hygiene work.

What Is LEV Testing?

LEV testing is carried out to assess whether a local exhaust ventilation system is operating as designed. This typically includes checking airflow, capture velocities, pressure drops, and system condition against its original design or commissioning criteria.

Under COSHH, LEV systems are required to be thoroughly examined and tested at suitable intervals — typically at least every 14 months — with records maintained as evidence of compliance. LEV testing therefore helps demonstrate that:

• The ventilation system is mechanically sound

• Air is being moved and captured as intended

• Basic performance criteria continue to be met

LEV testing is a legal requirement and a fundamental part of maintaining effective exposure control. It is a core service provided by occupational hygiene practices like NOHH Ltd and forms an important component of many workplace control strategies.

What LEV Testing Does Not Assess

LEV testing does not directly measure worker exposure. Specifically, it does not:

• Measure airborne contaminant concentrations in the breathing zone

• Account for how tasks are actually carried out day to day

• Capture variability in work practices or behaviour

• Confirm whether exposure is being adequately controlled in practice

For this reason, LEV testing alone may not always be sufficient to demonstrate that exposure is adequately controlled, particularly where occupational exposure limits apply, work patterns vary, or processes have changed. This does not represent a failure of LEV testing itself, but a limitation of what it is designed to show.

Why This Distinction Matters

LEV systems are often one element of a wider control strategy. Their effectiveness depends on:

• How they are used in practice

• Whether work methods align with design assumptions

• The nature of the substances being controlled

• Duration and frequency of exposure

LEV testing confirms system performance, whereas occupational hygiene work considers whether that performance is sufficient to control exposure. This distinction is particularly important during statutory engagement, including discussions with the HSE, where evidence of exposure control (not just system condition) may be expected.

How Occupational Hygiene Complements LEV Testing

Within occupational hygiene work, LEV testing is often used as one input among several. A qualified occupational hygienist may:

• Review LEV test results alongside exposure data

• Assess whether the system remains appropriate for the task

• Consider task variability and user behaviour

• Identify situations where actual exposure potential falls outside the scope of the LEV provided

In some cases, this may include targeted exposure monitoring to confirm whether LEV performance is delivering adequate control in practice. In this way, LEV testing supports interpretation and decision-making, rather than acting as a standalone conclusion.

Choosing the Right Level of Support

Not every situation requires the same level of input. In some cases, single-issue testing may be entirely appropriate. In others, a broader occupational hygiene approach is necessary. The key is ensuring that the scope of work matches:

• The complexity of exposure

• The potential health risk

• The need for defensible evidence

• Long-term operational objectives

Understanding the difference between occupational hygiene work and single-issue testing helps organisations choose support that is proportionate, effective and sustainable. Additional occupational hygiene input may be appropriate where:

• Processes, materials, or work practices have changed

• Exposure has not previously been assessed

• There is uncertainty around actual exposure levels

• Statutory feedback requests evidence beyond system condition

Here, LEV testing remains essential, but it is most effective when integrated into a broader occupational hygiene assessment strategy.

Taking a Proportionate Approach

Where LEV testing has been recommended or is due as part of statutory requirements, discussing scope and context early can help ensure results are interpreted appropriately and, where necessary, supported by wider occupational hygiene assessment.

NOHH Ltd provides statutory LEV testing alongside broader occupational hygiene services delivered by BOHS-qualified hygienists across the UK, supporting proportionate compliance and long-term exposure management. Contact us below for a free consultation from a qualified hygienist.