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The COSHH-specific hierarchy of control under Regulation 7, from elimination through to PPE, with worked examples of each level and the regulations that drive the order.
PPE is the last resort, not the first. That's the principle that runs through Regulation 7 of the COSHH Regulations 2002, and it's the principle most often broken in UK workplaces. Hand a worker a pair of gloves and a dust mask, and the controls feel done — when in fact the law expects you to have considered every other option first.
This page covers the COSHH hierarchy of control: what it is, where it comes from in the regulations, and what each level looks like in practice. For the broader picture, see what COSHH is, and for how the hierarchy fits into the assessment, see how to carry out a COSHH risk assessment.
Where the hierarchy comes from
Regulation 7 of the COSHH Regulations 2002 is the operational heart of the regulatory regime. It splits the duty to control exposure into two distinct stages.
Regulation 7(2) sets the prevention preference. Where reasonably practicable, exposure to a hazardous substance must be prevented — either by replacing the substance with one that's less hazardous, or by changing the process so the substance isn't needed at all. Prevention is the first thing the regulation requires you to consider, before any thought is given to controlling exposure.
Regulation 7(3) then sets out what to do where prevention isn't reasonably practicable. It establishes a hierarchy of control measures applied in order: engineering controls and appropriate work systems first; control of exposure at source and organisational measures next; and personal protective equipment only as a last resort, in combination with other controls.
This is the COSHH-specific hierarchy. It differs from the generic "elimination, substitution, engineering, administrative, PPE" pyramid used in general health and safety training. The COSHH version is structurally similar but legally tighter — substitution sits in its own regulation as the explicit prevention preference under Reg 7(2), and PPE is positioned not just as the lowest tier but as a control that must be used in addition to others, never alone.
For carcinogens, mutagens and substances that cause occupational asthma, the standard is higher still. Exposure must be reduced as low as is reasonably practicable (ALARP), regardless of whether a workplace exposure limit exists or has been met. The hierarchy still applies, but the bar is raised throughout.
Level 1: Eliminate the substance
Elimination means removing the hazardous substance from the workplace entirely. It's the most reliable form of control because the hazard no longer exists — no exposure is possible if the substance isn't there.
In practice, full elimination is rare. Most hazardous substances are in use because they do a job no harmless alternative can match. But it's worth asking the question. A workshop using a hazardous degreasing solvent for parts cleaning may discover that ultrasonic cleaning with water and detergent achieves the same result. A laboratory using a particular reagent may find that an automated kit with sealed cartridges removes the manual handling step entirely.
When elimination is genuinely possible, it removes not just the exposure risk but all the consequential duties — no monitoring, no health surveillance, no emergency arrangements specific to that substance, no substance-specific storage requirements. The compliance burden disappears with the substance.
Level 2: Substitute with something less hazardous
Substitution is the Regulation 7(2) preference. Where the substance can't be eliminated, the next question is whether it can be replaced with something less hazardous. "Less hazardous" can mean several things:
- A substance with a lower hazard classification (replacing a category 1 carcinogen with a category 2, or with a non-carcinogen)
- A different physical form of the same substance (pellets or granules instead of fine powder, removing the dust hazard)
- A more dilute formulation (10% acid solution instead of 36%)
- A different chemistry achieving the same outcome with fewer hazards (water-based instead of solvent-based)
The legal test is "reasonably practicable" — meaning the cost, effort and disruption of substitution must not be grossly disproportionate to the reduction in risk. Substituting a £5 paint for a £200 paint with marginally better hazard profile isn't reasonably practicable; substituting a known carcinogen for a non-carcinogenic alternative usually is.
Substitution requires care. The replacement substance has its own hazards, which need their own assessment. A water-based paint may eliminate solvent exposure but introduce a biocide. A new pellet form of a cleaning chemical may eliminate dust but be more concentrated, raising the consequences of accidental ingestion. The right test isn't "is the new substance less hazardous in general" but "is the overall risk lower in our specific context".
Level 3: Engineering controls
Engineering controls reduce exposure without depending on the worker doing anything different. They're built into the workplace and they work whether the worker is paying attention or not. That's why they sit above administrative controls in the hierarchy — they don't rely on consistent human behaviour.
The main engineering controls in COSHH practice are:
Total enclosure
The hazardous process is sealed within a container or chamber, with no opening through which substance can escape. Used for the highest-risk substances — isolators in pharmaceutical compounding, glove boxes for radiochemistry, sealed reactors in industrial chemistry.
Partial enclosure
The process is enclosed except where it has to be accessed. Spray booths for paint spraying, fume cupboards in laboratories, walk-in extraction enclosures for welding. Worker access is controlled by the enclosure geometry.
Local exhaust ventilation (LEV)
Air is extracted from the immediate vicinity of the source, before the substance can spread into the worker's breathing zone. The captured air is either filtered and recirculated, or discharged externally with appropriate treatment. LEV is the most common engineering control in UK workplaces. HSE's HSG258 is the authoritative guidance on designing, installing and maintaining LEV systems.
Dilution ventilation
General ventilation increases airflow through a workplace so any substance released is diluted below harmful concentrations. Less reliable than LEV because it depends on room geometry and airflow distribution, but useful for low-level releases over a wide area.
LEV systems must be thoroughly examined and tested at intervals not exceeding 14 months under Regulation 9 of COSHH. This is a specific operational requirement that catches out many workplaces — an LEV system overdue its test is technically non-compliant regardless of how well it appears to be working.
Level 4: Control at source and organisational measures
Where engineering controls reduce but don't eliminate exposure, organisational measures fill the gap. They focus on how the work is done rather than the equipment used.
The main approaches:
Limit access
Restrict the people who can enter areas where the substance is used, to reduce the number exposed. Hot work permits, controlled access to chemical stores, sign-in procedures for laboratory areas.
Limit the duration of exposure
Job rotation so individual workers spend less time in higher-exposure roles. Maximum exposure periods for specific tasks, with breaks in low-exposure areas.
Reduce the quantity in use
Decant smaller working quantities from bulk storage, so the maximum quantity that could be released in any incident is limited. Move dispensing operations to dedicated areas.
Schedule high-exposure tasks for low-occupancy periods
A fume-generating task done at the end of a shift, when fewer workers are present, exposes fewer people overall.
Separate clean and dirty areas
Workers don't carry contamination into rest areas, food storage or offices. Changing rooms, hand-washing facilities and decontamination procedures keep exposure contained where it originates.
Level 5: Administrative controls
Administrative controls are procedures, signs, training and supervision. They depend on the worker knowing what to do and doing it consistently — which is why they sit below engineering controls in the hierarchy. A perfect procedure that workers ignore protects no one.
The standard administrative controls under COSHH include:
- Written safe operating procedures for each substance and process
- Workplace signage at storage areas, use points and process equipment
- Training on the substances, the controls, the procedures and emergency response — see COSHH responsibilities for employers and employees for the full duty under Regulation 12
- Supervision to check that procedures are followed in practice
- Permit-to-work systems for higher-risk tasks
- Health surveillance and monitoring records that feed back into adjustments to the system
Administrative controls work best when combined with engineering controls. The engineering control reduces the consequence of a procedural failure; the procedural control reduces the frequency of failure in the first place.
Level 6: Personal protective equipment
PPE is the bottom of the hierarchy because it has the most failure modes. Engineering controls work all the time; PPE only works when the worker is wearing it correctly, when it fits, when it's in good condition, and when it's the right type for the substance.
That said, PPE is often necessary in addition to other controls — even a well-designed LEV system doesn't eliminate the residual exposure that engineering controls can't reach. The legal position is that PPE is acceptable as a control measure provided it's used in combination with other controls, not instead of them.
Specific PPE requirements vary by substance and use. Some general standards:
- Chemical-resistant gloves are specified to BS EN ISO 374. The Type A, B and C designations indicate the resistance to listed chemicals; the specific glove material (nitrile, neoprene, butyl, PVC) must match the substance from Section 8 of the safety data sheet — see COSHH safety data sheets for the full structure
- Respiratory protective equipment (RPE) comes in many types. Disposable filtering facepieces are specified to BS EN 149 (FFP1 through FFP3, with FFP3 the highest protection). Reusable half-mask and full-mask respirators take replaceable cartridge filters specified to BS EN 14387 for gases and combined filters, and BS EN 143 for particulate filters
- Eye and face protection comes under BS EN 166 for the safety frame, with additional standards for specific filter functions (UV, infrared, laser)
- Chemical protective clothing is specified to a range of BS EN standards depending on the level of protection (Type 1 gas-tight through Type 6 light splash)
For tight-fitting respiratory PPE, face-fit testing is a legal requirement. A respirator that doesn't seal against the face provides little protection regardless of its filter rating. HSE expects face-fit testing through either qualitative (taste test) or quantitative (particle count) methods, performed by a competent tester. The test must be repeated whenever the wearer's facial structure changes — significant weight loss or gain, facial hair, dental work.
How the hierarchy feeds into the risk assessment
The hierarchy structures Step 4 of the COSHH risk assessment — deciding what controls to use for each substance. The assessment process works through the hierarchy in order:
- Can the substance be eliminated or substituted? (Regulation 7(2) preference)
- If not, what engineering controls reduce exposure at source?
- What organisational measures supplement the engineering controls?
- What administrative controls govern how the work is done?
- What PPE is needed in addition to the above?
The output records the controls at each level and the reasoning for choosing them — particularly any level skipped, with the justification for why it wasn't reasonably practicable. An assessment that jumps straight to PPE without considering substitution or engineering controls won't survive scrutiny from an HSE inspector.
Workers need to understand the hierarchy too. Knowing why PPE is the last resort changes how people use it — workers who understand that their gloves and mask supplement engineering controls treat them differently from workers who think the gloves are the only thing between them and the substance. That's part of the Regulation 12 training duty and one of the topics covered in structured COSHH Training.
Frequently asked questions
What's the difference between elimination and substitution?
Elimination removes the hazardous substance from the workplace entirely — no exposure is possible because the substance isn't there. Substitution replaces it with a less hazardous alternative. The alternative still has hazards, but at a lower level. Both come before engineering controls in the hierarchy, with elimination preferred where it's possible.
Why is PPE the last resort?
PPE has more failure modes than the other control levels. It depends on the worker using it correctly, on it fitting properly, on it being in good condition, and on it being the right type for the substance. Engineering controls work continuously and independently of worker behaviour; PPE only works when actively and correctly worn.
What's the difference between the COSHH hierarchy and the general hierarchy of control?
The general hierarchy ("elimination, substitution, engineering, administrative, PPE") is a single five-level pyramid used across all health and safety. The COSHH hierarchy is structured by Regulation 7 — substitution is the explicit prevention preference under Reg 7(2), and the remaining controls fall under Reg 7(3) as an ordered hierarchy. The underlying logic is the same; the legal framework is COSHH-specific.
Do I have to apply every level of the hierarchy?
You have to consider every level, in order, and document why each was or wasn't used. Skipping straight to PPE without considering whether engineering controls or substitution could work is the most common failure. An HSE inspector will look for evidence of consideration at each level, even where the eventual control was a combination from several levels.
