MDHS 82/2 The Dust Lamp

One of the Most Powerful Qualitative Tools Available to LEV Engineers and Occupational Hygienists

LEVCentral Expert Commentary

There are very few occupational hygiene tools that can completely change the way someone thinks about airborne exposure.

The Dust Lamp is one of them.

MDHS 82/2 – The Dust Lamp: A Simple Tool for Observing the Presence of Airborne Particles is one of HSE’s most influential publications for anyone involved in Local Exhaust Ventilation (LEV), occupational hygiene or exposure assessment. Rather than measuring dust concentrations, it describes how a powerful beam of light can be used to make normally invisible airborne particles visible, allowing engineers to observe how contaminants are released, transported and controlled within the workplace.

The guidance explains that many of the particles responsible for occupational disease—particularly the respirable fraction—cannot normally be seen with the naked eye. By using a correctly positioned high-intensity beam of light (often referred to as a Tyndall Beam or Dust Lamp), these particles become visible, allowing the effectiveness of engineering controls to be assessed qualitatively.

For LEV engineers, this document is indispensable.

It demonstrates that a dust lamp is far more than an impressive visual aid. Used correctly, it becomes a powerful investigative tool capable of revealing contaminant escape, ineffective hood capture, leakage from ductwork, poor work practices and unexpected airflow patterns that may never be identified by airflow measurements alone.

View HSE Guide

Original HSE Guide

Key Learning Points

MDHS 82/2 explains:

The principles of the dust lamp.
The science of light scattering (Tyndall effect).
Why respirable particles are normally invisible.
How fine airborne particles behave.
Selecting suitable lighting equipment.
Correct positioning of the lamp.
Optimum viewing angles.
Background lighting considerations.
Qualitative assessment of airborne dusts, fumes, fibres and mists.
Observing contaminant movement.
Assessing LEV hood performance.
Identifying leakage from processes and control systems.
Recording observations using photography and video.
The advantages and limitations of the technique.
Why the dust lamp should be used alongside, not instead of, quantitative exposure monitoring.

Typical Applications

The guidance describes numerous practical uses for the dust lamp, including:

Application	Benefit
LEV Commissioning	Demonstrates whether contaminants are being captured effectively at source.
Thorough Examination & Testing (TExT)	Provides valuable qualitative evidence to support quantitative measurements.
Occupational Hygiene Surveys	Identifies previously unrecognised sources of exposure.
Process Assessment	Reveals how contaminants move through the workplace.
Training	Makes invisible hazards immediately visible to workers and managers.
Fault Finding	Identifies leaks, poor hood positioning and ineffective work practices.
Housekeeping Audits	Demonstrates how settled dust becomes re-entrained into the air.

Source Document Information

Organisation: Health and Safety Executive (HSE)

Document: MDHS 82/2 – The Dust Lamp: A Simple Tool for Observing the Presence of Airborne Particles

Series: Methods for the Determination of Hazardous Substances (MDHS)

Document Type: HSE Technical Guidance

Primary Topics: Dust Lamps, Tyndall Beam, Occupational Hygiene, LEV, Exposure Assessment, Qualitative Airborne Dust Assessment.

Audience: Occupational Hygienists, LEV Designers, LEV Commissioning Engineers, LEV Test Engineers, Health & Safety Professionals, Employers and Duty Holders.

LEVCentral Perspective

In our opinion, every LEV engineer should own and regularly use a dust lamp.

No other inexpensive tool demonstrates airborne contaminant behaviour so effectively.

Throughout our BOHS training courses, delegates are often surprised to discover that processes which appear “clean” under normal lighting can produce extensive clouds of respirable dust when viewed using a dust lamp. Equally, extraction systems that appear to be functioning satisfactorily can sometimes be shown to allow significant contaminant escape.

One of the greatest strengths of the technique is its ability to bridge the gap between engineering measurements and real workplace exposure.

A Pitot tube may confirm that the duct velocity is correct.

An anemometer may confirm the required face velocity.

But only the dust lamp shows whether the contaminant is actually entering the hood.

This distinction is fundamental.

Successful LEV is not about achieving a particular airflow value—it is about capturing hazardous substances before they reach the worker’s breathing zone.

The guidance also makes an important point that is sometimes overlooked. A dust lamp does not measure exposure. It provides a qualitative assessment, allowing engineers to identify where contaminants are released and how they move. Where quantitative exposure assessment is required, suitable air sampling methods remain essential.

Further Resources

Recommended Learning

Thought Leadership

There is a saying often used during LEV training:

“If you can make the invisible visible, you have already solved half the problem.”

That is precisely what the dust lamp achieves.

Many occupational diseases are caused by contaminants that workers cannot see. Respirable dust, welding fume, oil mist and many process aerosols remain almost invisible under normal lighting conditions, leading employers to underestimate exposure. The dust lamp removes that uncertainty by allowing engineers, managers and operators to observe airborne contaminants directly.

Perhaps its greatest value, however, lies not in technical assessment but in behavioural change. Few training demonstrations are as powerful as showing a worker the cloud of respirable dust entering their breathing zone despite appearing invisible only moments earlier. The impact is immediate and memorable.

From a LEVCentral perspective, MDHS 82/2 is one of the most important guidance documents ever published for LEV practitioners. It reminds us that while airflow measurements and pressure readings are essential, the ultimate purpose of any LEV system is simple: prevent hazardous airborne contaminants from reaching people.

The dust lamp allows us to see whether that objective is truly being achieved.