Principles of prevention and hierarchy of controls

Why the hierarchy of controls matters

The hierarchy of controls is perhaps the most important concept in practical health and safety management. It provides a systematic approach to deciding how to control workplace risks, working from the most effective measures (eliminating the hazard) down to the least effective (personal protective equipment).

This is not just good practice - it has a legal basis. Regulation 4 of the Management of Health and Safety at Work Regulations 1999 requires employers to implement preventive and protective measures on the basis of the general principles of prevention set out in Schedule 1.

The hierarchy of controls

Schedule 1 lists nine principles of prevention in priority order. They start with avoiding risks and combating them at source, and they give collective protection priority over individual protection. In practice they are summarised as a hierarchy of controls, often remembered as ERICPD. Work down it in order:

1. Eliminate the hazard so no risk remains, for example by stopping the activity, removing the substance or redesigning the process.
2. Reduce the hazard by replacing it with something less dangerous, such as a safer chemical or lower-powered equipment.
3. Isolate people from the hazard with guards, enclosures, ventilation, interlocks or barriers.
4. Control exposure with safe systems of work, written procedures, permits to work, supervision, job rotation, training and signs.
5. Use personal protective equipment (PPE) only when the controls above are not reasonably practicable.
6. Apply discipline by supervising and checking that every control is used correctly.

Applying the hierarchy: worked examples

Hazardous substances

• Eliminate the substance if you can, for example by switching from a solvent-based to a water-based process.
• Reduce the hazard by substituting a less hazardous substance, such as a lower-toxicity cleaning product.
• Isolate the process in an enclosure and fit local exhaust ventilation (LEV) to extract fumes at source.
• Control exposure by limiting exposure time, rotating workers and using permit-to-work procedures.
• Use respiratory protection, gloves and goggles only if the controls above are not enough.

Working at height

• Eliminate work at height by doing the job from ground level, for example with a long-reach tool.
• Reduce the height and duration of any work at height.
• Isolate the risk with guardrailed platforms, scaffolding or mobile elevated work platforms (MEWPs).
• Control the work with safe systems of work, training and supervision.
• Use fall arrest harnesses only when collective protection is not reasonably practicable.

Noise

• Eliminate the noise by using a quieter process or quieter equipment.
• Reduce it with silencers, dampers or noise-reduced tools.
• Isolate the source in an enclosure and create noise refuges for workers.
• Control exposure by limiting exposure time and marking hearing protection zones.
• Use ear defenders or plugs, with proper selection, training and maintenance.

Links to specific regulations

The hierarchy of controls appears throughout UK health and safety regulations:

• COSHH 2002 sets an explicit hierarchy for controlling exposure to hazardous substances.
• The Manual Handling Operations Regulations 1992 require you to avoid, assess and reduce.
• The Work at Height Regulations 2005 require you to avoid, prevent and minimise.
• The Control of Noise at Work Regulations 2005 require you to eliminate, control and then provide PPE.
• The Control of Vibration at Work Regulations 2005 require you to eliminate, reduce and then provide PPE.

In each case, the legal structure reflects the same principle: deal with hazards at source before relying on individual protection.