Strengthening Workplace Hazard Management Under the Hierarchy of Control

Under the Control of Substances Hazardous to Health (COSHH), employers are legally required to prevent exposure to hazardous substances where reasonably practicable, or where prevention is not possible, to control exposure to as low as reasonably practicable (ALARP). 

However, meeting this obligation demands more than just the identification of potential hazards. It requires site managers, health and safety professionals, and supervisors to conduct structured evaluations of how exposure arises in the first place, and whether control measures are capable of protecting workers. Moreover, detailed assessments should be conducted by qualified and certified individuals, or at least under the oversight of a competent person as defined under COSHH.

Central to this approach is the Hierarchy of Control. Embedded within the majority of COSHH guidance, this framework establishes a clear order of priority for hazard control and risk management, emphasising hazard elimination or specific engineering controls in tandem with administrative measures, before resorting to personal protective equipment as a default.

Many professionals responsible for COSHH compliance are familiar with these aspects of the hierarchy in principle, but applying them effectively within complex, real-world operational environments requires technical judgement that balances business needs against achievement of meaningful risk reduction. Understanding how the hierarchy underpins COSHH decision-making is the first step before examining how it can be applied in practice.

The Hierarchy of Control

The hierarchy is designed to establish a structured order of priority for selecting control measures. At the top are measures that prevent exposure entirely or control it at source, and at the base are measures that rely on individual behaviour or protection:

• Elimination sits at the highest level and deploys the principle that by removing the hazardous substance or process entirely, exposure cannot occur. An example may be discontinuing the use of a particular hazardous chemical or redesigning a task or process to remove any need for it.
• Substitution follows, based on the idea that replacing a hazardous material or activity with a safer alternative reduces the risk to health. For example, switching from a highly volatile toxic solvent to a less volatile and/or lower toxicity solvent that can deliver similar results.
• Engineering controls aim to isolate workers from the hazard by using physical or mechanical systems to reduce exposure. This is achieved through containment systems, process enclosures, or specialised local exhaust ventilation (LEV) designed to capture contaminants at source.
• Administrative controls influence how work is organised, including task rotation, restricted access to high-risk areas, isolation measures, or revised procedures that limit the duration or frequency of exposure.
• Personal protective equipment sits at the lowest level of the hierarchy, providing individual protection through respirators, masks, gloves or protective clothing.

This progression reflects clear differences in how each control level reliably manages risk, which means that applying the hierarchy effectively depends on recognising and responding to those distinctions in practice.

Applying the Hierarchy in Practice

Within the Hierarchy of Control, personal protective equipment sits at the lowest level within the hierarchy because this measure is intended to be used in situations where exposure cannot be adequately prevented or controlled through higher-level measures. This reflects a key principle within COSHH: the most effective controls address the hazard at its source, preventing exposure from occurring rather than attempting to manage its consequences.

Controls at source such as elimination, substitution, or well-designed engineering, offer greater reliability because protection is embedded within the process itself. Their effectiveness does not depend on individual behaviours, correct fit, or consistent use. By contrast, PPE requires appropriate selection, checking, and maintenance all whilst leaving the underlying hazard unchanged. PPE also has a limited lifespan, needs frequent replacement, and may fail or underperform during use. In reality, the circumstances driving its use should be under frequent review so as to reduce future dependency, rather than accepting PPE use as default.

For those responsible for hazardous substance management, this distinction has practical implications. COSHH clearly states that dutyholders must demonstrate that prevention and higher-level controls have been fully considered and implemented before reliance is placed on administrative measures or PPE. The hierarchy therefore operates as a structured decision-making framework, guiding how exposure should be reduced at source wherever reasonably practicable.

However, applying this framework to complex, evolving workplace processes requires careful navigation of technical and operational challenges.

Technical and Operational Challenges

In practice, implementing higher-order controls requires an understanding of how hazards behave within specific workplace processes. Engineering controls must be designed to function within the realities of production environments, where substances may be generated intermittently or handled across different tasks. Moreover, they must also work properly and deliver constant performance. For example, the effectiveness of containment systems or local exhaust ventilation depends not only on their presence, but on correct positioning, airflow performance, and long-term maintenance.

Control strategies must also account for the limitations of certain approaches. Dilution ventilation may help reduce background contaminant levels in some settings, yet it provides limited protection where higher concentrations are generated close to the source. Under COSHH, dutyholders are expected not only to select appropriate controls, but to verify that they are working as intended and to review them as processes change or new materials are introduced.

In many workplaces, responsibility for managing hazardous substances sits with safety managers or technical specialists whose roles encompass multiple operational and compliance responsibilities. As a result, these professionals may inherit COSHH control responsibilities without formal education in hazard control design or evaluation. Yet under COSHH, these professionals must also be able to demonstrate appropriate competence, or risk regulatory enforcement or legal action.

Strengthening technical knowledge and judgement therefore becomes essential to ensuring that control strategies remain aligned with regulatory expectations and provide reliable protection for those exposed.

Building Competence Through Specialist Training

It is clear that managing hazardous substances effectively relies on applying the Hierarchy of Control with confidence and technical understanding. Under COSHH, dutyholders must be able to evaluate complex processes, determine which control measures are appropriate, and demonstrate that those decisions are justified. Developing the knowledge and confidence to do this consistently is therefore an important part of professional competence.

Structured training provides a practical way to strengthen this capability. The BOHS M505 Control of Hazardous Substances course is designed to develop a deeper understanding of how control measures should be selected, justified, and evaluated under COSHH. This includes how exposure can be prevented at source, how engineering controls function in practice, and how their effectiveness should be verified over time. For safety managers and technical specialists, this type of training strengthens the ability to make well-reasoned control decisions and maintain alignment with regulatory expectations.

Envirochem delivers BOHS-accredited occupational hygiene designed to build this level of structured technical competence. As a BOHS-recognised provider and UKAS-accredited consultancy, our courses are led by highly experienced practitioners and delivered in-person, with small class sizes to support focused discussion and practical understanding. Ongoing support through to final assessment helps participants build the confidence and technical judgement required to apply the Hierarchy of Control effectively within their own organisations.

To learn more about Envirochem’s occupational hygiene training programmes, visit our Occupational Hygiene Qualification Courses page. Details of upcoming course dates are available by contacting our training team at training@envirochem.co.uk.