L5 – Control of Substances Hazardous to Health (CoSHH)

The CoSHH Regulations, Approved Code of Practice (ACOP) and Guidance – The Foundation of Occupational Hygiene and LEV in Great Britain

LEVCentral Expert Commentary

If there is one publication that every employer, Duty Holder, occupational hygienist and LEV engineer should own, it is L5 – Control of Substances Hazardous to Health.

This document is not simply guidance.

It contains three documents in one publication:

The Control of Substances Hazardous to Health (COSHH) Regulations 2002 (as amended) – the law.
The Approved Code of Practice (ACOP) – practical guidance with a special legal status.
HSE Guidance – detailed explanations and examples to help duty holders comply with the Regulations.

Everything that follows in LEV engineering ultimately stems from this publication.

HSG258 explains how to design, commission and maintain LEV systems.

MDHS methods explain how to measure exposure.

EH40 specifies Workplace Exposure Limits.

COSHH Essentials provides task-specific control guidance.

But it is L5 that establishes why these activities are legally required.

For anyone involved in controlling airborne contaminants, this is arguably the single most important health and safety publication produced by the HSE.

View Original Publication

View CoSHH & ACOP L5

What Makes L5 So Important?

Unlike many HSE publications, L5 combines three different levels of information.

Section	Purpose
The Regulations	The legal duties placed upon employers and others under COSHH.
Approved Code of Practice (ACOP)	Practical guidance that has a special legal status. Following the ACOP is normally sufficient to demonstrate compliance with the law. If an alternative approach is used, it must achieve at least an equivalent standard of protection.
HSE Guidance	Detailed explanations, examples and good practice to help duty holders understand and comply with the Regulations.

This combination makes L5 much more than a guidance document—it is the principal reference explaining how COSHH should be applied in practice.

Key Learning Points

L5 explains every aspect of COSHH, including:

What constitutes a hazardous substance.
Employer duties.
COSHH risk assessment.
Prevention of exposure.
Adequate control of exposure.
The hierarchy of control.
Principles of Good Practice.
Local Exhaust Ventilation (LEV).
Process enclosure.
General ventilation.
Personal Protective Equipment (PPE and RPE).
Maintenance of control measures.
Thorough Examination and Testing of LEV.
Exposure monitoring.
Health surveillance.
Information, instruction and training.
Occupational Exposure Limits.
Biological agents.
Carcinogens.
Mutagens.
Respiratory sensitisers.
Emergency arrangements.
Record keeping.
Enforcement expectations.

The Eight Principles of Good Practice

Perhaps the most influential part of L5 is Schedule 2A, which sets out the Eight Principles of Good Practice for the Control of Exposure to Substances Hazardous to Health.

Every COSHH risk assessment and every LEV system should ultimately support these principles:

Design and operate processes to minimise emission, release and spread of hazardous substances.
Take account of all relevant routes of exposure.
Control exposure by measures proportionate to the health risk.
Choose the most effective and reliable control options.
Where adequate control cannot otherwise be achieved, provide suitable respiratory protective equipment.
Check and review all elements of control measures regularly.
Inform and train employees on the hazards and controls.
Ensure that control measures continue to minimise exposure.

These principles underpin virtually every modern approach to occupational hygiene and LEV.

Source Document Information

Organisation: Health and Safety Executive (HSE)

Publication: L5 – Control of Substances Hazardous to Health

Edition: Sixth Edition (2013)

Series: Approved Code of Practice (L Series)

Document Type: Regulations, Approved Code of Practice and Guidance

Primary Topics: COSHH, Occupational Hygiene, Local Exhaust Ventilation, Exposure Control, Risk Assessment, Health Surveillance, Workplace Exposure Limits.

LEVCentral Perspective

From an LEVCentral perspective, everything begins with COSHH.

Many people think LEV is about fans, ductwork and airflow measurements.

It is not.

LEV exists for one reason only:

To help employers comply with Regulation 7 of COSHH by preventing or adequately controlling exposure to substances hazardous to health.

This distinction is important.

A technically impressive extraction system has little value if it does not adequately control exposure.

Conversely, a relatively simple system that consistently achieves adequate control is entirely consistent with COSHH.

L5 also makes clear that LEV should never be considered in isolation.

The Regulations require employers to consider:

elimination;
substitution;
process design;
enclosure;
automation;
engineering controls;
safe systems of work;
maintenance;
health surveillance;
information, instruction and training.

LEV is one element—albeit a very important one—within a much broader occupational hygiene management system.

One of the most overlooked aspects of L5 is its emphasis on adequate control rather than simply compliance with Workplace Exposure Limits. For substances such as respiratory sensitisers, carcinogens and mutagens, employers are expected to reduce exposure as low as is reasonably practicable (ALARP), even where exposure is below the published limit. This principle has profound implications for LEV design, commissioning and ongoing management.

Further Resources

This publication sits at the centre of the UK’s occupational hygiene framework and should be read alongside:

Recommended Learning

Thought Leadership

There is a tendency within industry to think of COSHH as a paperwork exercise centred around risk assessments.

L5 demonstrates that COSHH is something far more important.

It is a management system for protecting health.

Every hood designed, every LEV system commissioned, every workplace exposure measurement, every health surveillance programme and every Thorough Examination and Test ultimately serves a single objective:

Preventing people from becoming ill through exposure to hazardous substances.

That philosophy runs throughout L5.

From a LEVCentral perspective, this publication is the cornerstone upon which almost every other occupational hygiene and LEV document is built. HSG258 explains how to manage LEV. MDHS methods explain how to measure exposure. COSHH Essentials explains how to control specific tasks. But L5 provides the legal and practical framework that binds them all together.

If an LEV professional were asked to own just one HSE publication, this would almost certainly be the one. It is the document that defines not only what the law requires, but also the principles that have shaped occupational hygiene practice in Great Britain for more than two decades.