Legionnaires' Disease: Control of Legionella Bacteria in Water Systems

This book is aimed at duty holders, including employers, those responsible for property control, and others with health and safety responsibilities. Its purpose is to help them comply with their legal obligations related to legionella. These obligations include identifying and assessing risk sources, preparing a plan to prevent or control the risk, implementing, managing, and monitoring measures, keeping records of measures, and appointing a manager responsible for others.

The fourth edition of this ACOP and regulatory guidance includes revisions to simplify and clarify the text. The main changes are:

  • Removal of the technical guidance in Section 2; this guidance has been published separately as HSG274.
  • ACOP status has been given to the following topics:
    • Risk assessment;
    • The special role of the appointed competent person, known as the "responsible person";
    • Control plan;
    • Review of control measures;
    • Duties and responsibilities of those involved in the supply of water systems.

About the Approved Code of Practice (ACOP) and Guidance

This Code has been approved by the Health and Safety Executive (HSE) with the Minister's approval. It provides practical advice for compliance with the law. Following the advice means compliance with the law on the relevant matters. Alternative methods may be used, but the Code has a special legal status. If health and safety laws are breached, and it is proven that the relevant provisions of the Code were not followed, the court will require proof that the law was complied with in another way.

The guidance is published by the HSE. Compliance with the guidance is not mandatory but usually ensures compliance with the law. Health and safety inspectors may refer to this guidance to ensure compliance.

Contents

  • Introduction
  • About This Book
  • About ACOPs
  • Presentation
  • Legionnaires' Disease
  • Health and Safety Law
  • Scope and Application
  • Identification and Assessment of Risk
  • Carrying Out Risk Assessment
  • Risk Management: Management Responsibilities, Training and Competence
  • Competence
  • Implementation of the Control Plan
  • Prevention or Control of Risk from Exposure to Legionella Bacteria
  • Review of Control Measures: Monitoring and Routine Inspection
  • Record Keeping
  • Responsibilities of Designers, Manufacturers, Importers, Suppliers and Installers
  • Appendix 1: Approval Notification
  • Glossary of Terms
  • Sources and Further Reading
  • Additional Information

Introduction

About This Book

This Approved Code of Practice (ACOP) provides advice on the legal requirements concerning the risk of exposure to legionella bacteria under the 1974 Health and Safety at Work etc. Act (HSW Act) and the 2002 Control of Substances Hazardous to Health Regulations (COSHH). It specifically guides compliance with sections 2, 3, 4, and 6 of the HSW Act and regulations 6, 7, 8, 9, and 12 of COSHH. It also covers compliance with relevant parts of the 1999 Management of Health and Safety at Work Regulations.

The book is intended for duty holders such as employers and those responsible for property control (e.g., landlords). To fulfill their legal obligations, duty holders must:

  1. Identify and assess risk sources. This includes checking for conditions that encourage bacterial growth. For example, if water temperature is between 20–45 °C, if there are systems that can create and spread aerosols (such as cooling towers, showers, spa pools), and if vulnerable people at risk are exposed to these aerosols.
  2. If appropriate, prepare a written plan to prevent or control the risk.
  3. Implement, manage, and monitor measures. Regular monitoring of systems and measures is necessary to ensure control measures remain effective. Monitoring total bacterial counts can indicate whether microbiological control is maintained; legionella sampling is another way to check if the system is under control.
  4. Keep records of the measures.
  5. Appoint a competent person with sufficient authority and installation knowledge to ensure compliance with the law.

The guidance also specifies the responsibilities of water system service providers and system designers, manufacturers, importers, suppliers, and installers.

The fourth edition includes revisions to simplify and clarify the text. The main changes are:

  • Removal of the technical guidance in Section 2 and its separate publication as HSG274 (Section 1: Evaporative cooling systems; Section 2: Hot and cold water systems; Section 3: Other risk systems).
  • Granting ACOP status to the following topics:
    • Risk assessment;
    • The role of the appointed competent person ("responsible person");
    • Control plan and its content;
    • Review of control measures;
    • Duties and responsibilities of those involved in the supply of water systems.

About ACOPs

ACOPs are approved by the HSE Board with the Minister's approval. They explain preferred or recommended methods and standards for compliance with the law. The guidance provides advice, general information, technical details, and references to additional information sources to ensure compliance.

The legal status of the ACOP and guidance text is clearly stated on page 2.

Presentation

The ACOP text is shown in bold, guidance text in normal type, and regulation references in italics. Colored boxes clearly separate each section. After each regulation reference, a brief summary of the main duties imposed by that regulation is provided. These summaries are for information only and do not have ACOP or guidance status.

Legionnaires' Disease

Legionellosis is the general term for diseases caused by legionella bacteria. The most serious is Legionnaires' disease; similar but less severe illnesses include Pontiac fever and Lochgoilhead fever. Legionnaires' disease is a potentially fatal form of pneumonia, and everyone is susceptible to infection. Risk increases with age; people over 45, smokers, heavy drinkers, those with chronic respiratory or kidney disease, diabetes, lung and heart disease, or weakened immune systems are at higher risk.

Legionella pneumophila and related bacteria are common in natural water sources (rivers, lakes, reservoirs) but usually in low numbers. They can also be found in artificial water systems such as cooling towers, evaporative condensers, hot and cold water systems, and spa pools. When suitable conditions arise, bacteria can multiply, increasing the risk of Legionnaires' disease. Therefore, controlling risks with appropriate measures is important.

Although legionella bacteria are widespread in natural water systems, disease transmission from these sources is rare. Disease usually spreads from artificial systems that maintain water between 20–45 °C and can create and disperse aerosols.

Legionnaires' disease is typically transmitted by inhaling small water droplets (aerosols) containing the bacteria. Risk increases when:

  • Water temperature is between 20–45 °C throughout or in parts of the system;
  • Water droplets can form and spread;
  • Water is stored or recirculated;
  • Deposits such as rust, sludge, scale, organic matter, and biofilm that support bacterial growth are present.

To control risks, measures must be taken in water systems to prevent bacterial growth and reasonably reduce exposure to water droplets.

Health and Safety Law

Obligations under the HSW Act apply to risks of legionella exposure arising from work activities. The Management Regulations provide the general framework for health and safety. They require risk assessments, competent assistance for employers, procedures for serious and imminent dangers, and cooperation and coordination when multiple employers or self-employed persons share a workplace.

COSHH provides a framework to control risks from hazardous substances, including biological agents. Key elements include:

  • Risk assessment;
  • Prevention of exposure or substitution with less hazardous substances or methods;
  • If prevention or substitution is not possible, control of exposure;
  • Maintenance, examination, and testing of control measures;
  • Provision of information, instruction, and training to employees;
  • Health surveillance where necessary.

The 2013 Reporting of Injuries, Diseases and Dangerous Occurrences Regulations (RIDDOR) require employers and those in control of workplaces to report work-related accidents and certain diseases to the HSE. Cases of legionellosis must be reported if a doctor notifies the employer and the employee's work involves cooling or water supply systems.

The Notification of Cooling Towers and Evaporative Condensers Regulations 1992 require those in control of workplaces to notify local authorities in writing about "notifiable devices." Notifiable devices are cooling towers and evaporative condensers where water is exposed to air.