Human factors: Maintenance error

Why is maintenance error important?

When we address human factors in relation to health and safety, we're aiming to optimise human performance and reduce human failures. Even experienced, highly-trained, well-motivated technicians can make simple slips and omissions, and such errors can initiate major accidents, as well as result in personal injury to maintenance personnel.

Maintenance quality is heavily reliant on human activity - many accidents and incidents have maintenance error as a root or major contributory cause. So, in addition to managing the safety of personnel undertaking maintenance, it is necessary to ensure that the actions and decisions of maintenance personnel do not leave the equipment or system in an unsafe state. Common maintenance failures include incorrect reassembly, wrong specification of replacement items, omission of a task step, re-commissioning errors, safety features left disconnected, instrument set-points incorrectly set or leaving tools inside.

However, human error in maintenance is largely predictable and therefore can be identified and managed. Furthermore, improvements in the reliability of maintenance will have business benefits beyond health and safety.

HSE expects all companies who undertake maintenance with the potential for severe consequences to be aware of the issue of human error and its importance. "Major hazard" or safety critical companies in particular will be expected to:

  • Have carried out an assessment (or be doing so);
  • Have a timed action plan;

. . . and so be able to demonstrate how maintenance error is considered.

Key principles in maintenance error

  • Design plant & equipment for maintainability (eg reduce complexity; improve accessibility; label plant and components; consider the working environment eg noise; temperature; lighting);
  • Conduct human error analysis on safety-critical maintenance tasks;
  • Consider the design of maintenance tasks (work is interesting and challenging; diagnostic tools are provided; adequate time is available; distractions are minimised; PPE is realistic etc.);
  • Develop up-to-date procedures for safety-critical maintenance tasks;
  • Involve all relevant maintenance personnel in plant & equipment design, job design, task analysis, writing procedures etc.;
  • Ensure supporting resources are readily available (P&IDs; schematics; job-aids; tools and spares etc.);
  • Provide effective communication channels between shifts, and between operations, maintenance and contractor personnel.

More information on maintenance error

  • Common topic 2: Maintenance error
  • Technical Measures Document – Maintenance Procedures
    This brief document provides guidance on assessing maintenance systems and usefully outlines where major hazards could arise during maintenance activities. It also links to several case studies illustrating the importance of managing maintenance systems.
  • Further information on Managing Human Failures
    including a 7-step risk assessment approach that many organisations have found useful.
  • Managing Maintenance Error: A Practical Guide, James Reason and Alan Hobbs (2003).
    A down-to-earth practitioner's guide to managing maintenance error. It deals with human risks generally and the special human performance problems arising in maintenance, as well as providing an engineer's guide for their understanding and the solution. ISBN: 978-0-7546-1591-0. Available from

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