RR836 – Perception and understanding of how local exhaust ventilation (LEV) works and how effective it is

LEVCentral Expert Commentary

A technically well-designed LEV system can still fail to protect workers if the people responsible for using and managing it do not understand how it works.

This important HSE research examined how employers, supervisors and operators perceive LEV systems and investigated whether common misconceptions contribute to poor performance and ineffective exposure control. The findings demonstrated that many users overestimate the effectiveness of LEV systems, misunderstand how contaminants are captured and transported, and often fail to recognise when systems are no longer operating effectively.

Rather than focusing on equipment design, RR836 highlights the human factors that influence LEV performance. It reinforces the principle that effective control depends not only on good engineering, but also on informed users, competent management and a clear understanding of system limitations.

Why this matters

Even correctly commissioned LEV systems can become ineffective if:

Operators position work incorrectly.
Hoods are moved away from the contaminant source.
Airflow indicators are ignored.
Maintenance issues go unreported.
Duty holders assume the system is “working” simply because the fan is running.

Understanding these behavioural factors is just as important as understanding airflow or hood design.

Source Document

Original HSE Guide

Source: Health and Safety Executive (HSE)
Document Type: LEV Research Report
Status: Current 2011
Last reviewed by LEVCentral: June 2026

Key Learning Points

The research identified several recurring themes, including:

Limited understanding of how LEV actually captures contaminants.
Overconfidence in the protection provided by extraction systems.
Poor appreciation of the importance of hood positioning.
Limited recognition of deteriorating system performance.
Inconsistent understanding of legal responsibilities.

The report concludes that improved education, clearer communication and better user training are essential if LEV systems are to deliver the level of protection expected.

LEVCentral Perspective

The findings in RR836 remain highly relevant today and align closely with LEVCentral’s approach to improving LEV competence.

Modern LEV management is no longer simply about installing extraction equipment. Effective control requires every stage of the LEV lifecycle to work together:

Good design
Correct installation
Independent commissioning
Competent operation
Planned maintenance
Thorough Examination & Testing
Informed duty holder management

Where understanding is lacking, even technically sound systems can fail to protect workers.

The report also reinforces why commissioning is so important. A comprehensive commissioning report provides duty holders with the knowledge and performance benchmarks needed to understand how their system should operate from day one. This directly supports the HSE’s current commissioning guidance, which places greater emphasis on documentation, performance benchmarks and user understanding.

Further Resources

Recommended Learning

Thought Leadership

Perhaps the most important message from RR836 is that LEV effectiveness depends as much on people as it does on engineering.

Many failures are not caused by poor fan performance or inadequate airflow, but by assumptions, misunderstandings and a lack of practical knowledge. Improving competence across the entire LEV lifecycle—from designers and commissioners through to supervisors and system users—remains one of the most effective ways of reducing occupational exposure and ensuring that LEV systems continue to deliver the protection they were designed to provide.