All property owners and management today must have and use a reliable Employers Guide to Legionella Risk Assessment & Control. It is extremely important for them to have full knowledge and understanding of the serious health hazards posed by Legionella and other harmful bacteria. Early detection of the presence of such serious hazards in building water supplies is vital to the wellbeing of everyone who inhabits, works at or spends time inside structures affected by dangerous bacteria. In addition, the Control of Substances Hazardous to Health Regulations 2002 (COSHH) offers extensive risk assessment, prevention and control guidelines relative to building contamination from Legionella and other health-endangering bacteria.1

The first known outbreak of Legionnaires’ disease occurred after attendees at an American Legion Convention in Philadelphia, PA, USA, were diagnosed with pneumonia in 1976. Samples of lung tissue from these patients revealed a mysterious type of bacteria. This bacterium was subsequently named Legionella pneumophila. Contamination occurred when patients inhaled the bacteria in water droplets or in water nuclei carried by moisture in the interior air supply of the hotel.

Common Legionnaires' Disease Symptoms and Diagnostic Procedures

Early symptoms of the disease include chills, persistent headaches, high fever and muscular discomfort. Patients may also experience difficulty in breathing and dry, raspy coughing. Other symptoms may be diarrhoea, nausea and increasing confusion or even delirium. Legionnaires’ disease has proven fatal to approximately 12% of known cases among otherwise healthy people, and to somewhat higher percentages of patients who have other serious or chronic illnesses or health conditions. The incubation period for this disease can range from two to ten days. Legionella bacterial infections can be successfully treated with antibiotics, and some patients develop only mild symptoms similar to those of common flu.

Legionnaires' disease can be diagnosed in bacteria from samples of sputum, bronchial tube washings and lung tissue. Patient urine and blood tests can also reveal the presence of Legionella infection. Pontiac fever and Lochgoilhead fever (named for an occurrence of the disease in Lochgoilhead, Scotland) are both mild forms of Legionella bacterial infection that can also be diagnosed by these testing methods.

Responsible Building Risk Assessment for Legionella Bacterial Infection

In addition to careful attention and adherence to a responsible Employers Guide to Legionella Risk Assessment & Control, the latest modern measures for identifying and evaluating contamination must be used. To insure accuracy in determining the sources and risk levels of Legionella contamination within your building’s interior environment, you may need to employ the expert services and advice of outside eco-conscious and green consultants.

Since hazardous Legionella bacteria can be found in natural bodies of water like rivers, streams, lakes and ponds, they can also be found within some building water storage tanks and distribution pipes. Because such dangerous bacteria can also be spread throughout building interior spaces by contaminated moisture in the air. When testing a building for Legionella contamination, it is essential to examine all areas of water storage and distribution throughout the entire facility. Testing should include all heat exchangers, pumps, baths and showers.

A careful and reliable examination for risk assessment of bacterial contamination in your building will include determining:

  • The extent to which water is kept in storage or circulated in your building; 
  • Whether or not the water temperature throughout your building’s water supply system is maintained at temperatures between 20◦ and 45◦C, the common range allowing the development and growth of Legionella and other harmful bacteria;
  • If there are existing conditions within your building water storage and circulation systems that encourage the formation and multiplying of harmful bacteria found in sludge, rust, scale and other organic substances;
  • Whether or not water droplets travel through your building air circulation system and are dispersed into the structure’s general interior atmosphere;
  • If there are employees who inhabit and work within your building now suffering from chronic illnesses or long-term health conditions that could be adversely affected by the possible release of bacterial contaminants into the building’s water or air circulation systems.

Guidelines for Prevention and Control of Legionnaires' Disease

After a thorough assessment of your building’s potential or present risk for contamination by Legionella and other harmful bacteria, the next step is to formulate and initiate strong measures for the prevention and control of these bacterial infections. As owner or manager of a building, it is your responsibility to hire or contract whatever skilled professionals and services are necessary to carefully initiate and control safety methods and procedures to best prevent bacterial contamination throughout the building. Whether you designate currently competent staff members to oversee and carry out this vital work or contract outside staffing, they must be well trained and experienced.

If thorough building interior examination and risk assessment reveal potential or real risks that you cannot eliminate, your staff or contracted professionals must take the appropriate actions to control and manage these risks. These necessary actions include:

  • Design a printed schematic for performing hazard prevention and control;
  • Identify the responsible individuals or team members of your building’s environmental hazards prevention and control plan along with their specific functions and duties; 
  • Define procedures for safe and responsible systems operations throughout your building facilities; 
  • Identify and explain all control methods, for example, cleaning and replacement of piping, water storage tanks and air circulation systems or units when needed;
  • Treat water to eliminate Legionella and other harmful microorganisms and maintain the cleanliness of your building’s water;
  • Use only the materials, piping structure, ducts, appliances and accessories that are officially approved for building use on the UK Water Supply System by the Water Regulations Advisory Scheme.


You must always maintain accurate records of your ongoing building water and air contamination prevention, control and management plans and operations. If you or the businesses housed within your real estate employ more than five employees, you must carefully record any problems cited. You are also obligated to correct these issues and to take all measures to ensure the health and safety of any staff members with serious illness or immune system deficiencies.

In compliance with the Notification of Cooling Towers and Evaporative Condensers Regulations 1992, as a building owner or operator you are required to inform the appropriate local officials in writing if your building makes use of an on-site evaporative condenser or cooling tower installation. Additionally, to comply with the Reporting of Injuries, Diseases and Dangerous Occurrences Regulations (RIDDOR), you are obligated to reveal all cases of employee Legionella infection if these individuals have at any time performed work on hot water systems or cooling tower structures that have been or are presumed to have been spreaders of Legionella bacteria. If your building contains spa pools, they must also be included in your water contamination prevention and control monitoring and reports.

There are many important aspects to carefully assessing, preventing, controlling and monitoring risk for contamination by Legionella bacteria in your building’s structures and spaces. Each separate aspect requires your diligent attention and action to ensure a healthy interior environment.

Author: +Duncan Hollis