The legionella challenge

Published:  04 April, 2012

B&ES, Amtech, legionella, Legionnaires' Disease

Modern Building Services has teamed up with the Building & Engineering Services Association (formerly the Heating & Ventilating Contractors’ Association) to share the knowledge and thinking of the organisation’s experts on a range of industry concerns and issues.

The number of cases of Legionnaires’ Disease is still rising around the world. Bob Towse explains how poor maintenance and complacency increases the risk of an outbreak and prosecution for the building owners and occupiers.

Deaths and serious illnesses resulting from Legionnaires’ Disease remain prevalent in hotels, hospitals and other public buildings, and are usually the consequence of poor maintenance regimes or complacency.

The causes and risks surrounding this very serious disease are well known, but the number of outbreaks continues to rise. There are around 300 reported cases in the UK every year, and 120 000 people are thought to have died in the USA since the cause of the disease was established there more than 30 years ago. [It was first identified and received its name following an outbreak among delegates at a meeting of the American Legion in a Philadelphia hotel in July 1976.]

The American Society of Heating, Air Conditioning & Refrigerating Engineers (ASHRAE) has produced a new standard that focuses on ensuring building operators have a system in place for managing the risk of legionella. They deliberately focused on the man- agement challenge as many of the technical solutions are already well established, but they are not deployed strategically or successfully in many instances.

A management challenge —  Bob Towse.


Bill McCoy, chair of the ASHRAE committee that produced the standard, told a recent HVCA webinar that the number of deaths around the world was ‘astonishing…for a wholly avoidable disease’. He said there had been a 217% increase in annually reported cases in the USA from 2000 to 2009.

Legal damages being claimed in US courts for exposure to legionella are simply huge. Eight claimants recently took a Las Vegas hotel to court for compensation of a staggering $337.5 million. So far, the largest payout in a US legionella ‘gross-negligence’ case is a mere $193 million!

10 years on from the notorious outbreak in Barrow-in-Furness, Cumbria, that led to seven deaths and another 180 people being taken ill, incidents of Legionnaires’ Disease in workplaces, hotels, hospitals and other public buildings are still occurring on a regular basis. Why?

It can partly be explained because the issue is better reported and diagnosis has improved, along with better detection techniques. Legionnaires’ Disease is a form of pneumonia, so it was often misdiagnosed in the past. However, there is also concern about mutation of the bacteria, some of which are now becoming resistant to higher temperatures and multiplying in lower temperatures.

Also, as the focus increases on saving energy, more building operators are switching off and/or turning down hot-water systems overnight and at weekends to save money and cut carbon emissions. This can lower the temperature of the stored hot water into the ‘danger zone’ between 20 and 50°C range, which is the ideal temperature range for legionella bacteria to thrive. The optimum temperature is thought to be 37°C.

The increasing use of solar-thermal heating systems can also, if the system is not properly controlled and maintained, result in more hot water being stored at temperatures that allow the bacteria to flourish before they are distributed into the air through taps and showerheads to be breathed in by building occupants.

Safety concerns about hot-water scalding have also led to an increase in blending-valve installations, which can lower hot-water temperatures into the legionella zone. Also, some strains of the bacteria can survive the low-level dosing of chlorine dioxide that is used in many facilities.

However, the general threat is poor maintenance and monitoring. Budgetary pressures have forced many facilities managers and building operators to reduce the frequency and thoroughness of system checks. In many instances, the vital initial risk assessment is also not carried out.

A regular programme of inspection and maintenance of air-conditioning, water-holding and water-supply systems is essential if future deaths from Legionnaires’ Disease are to be avoided. When clusters of cases occur they can typically be traced back to poorly maintained cooling-tower systems, air-conditioning plant or hot- and cold-water systems.


Risks can be dramatically reduced by setting up a programme of regular inspection and maintenance of susceptible plant and equipment including regular cleaning and disinfection. And this is not expensive — it is all about human vigilance.

Legal obligations for building owners and occupiers are set out in a single document, published by the Health & Safety Commission (HSC), called ‘Legionnaires’ Disease: the control of legionella bacteria in water systems’. This is an HSC Approved Code of Practice (ACoP), commonly referred to as L8.

It is the building owner’s responsibility to put a proper control strategy in place that includes managing the maintenance of water systems, regular monitoring (with the records kept for five years) and training for everyone in the management chain, with their skills updated periodically.

L8 is a legal document, so a building operator not following its instructions leaves a building operator open to legal action. It is also not enough to simply focus on cooling towers. The legionella bacteria can be present wherever water is used or stored. Avoiding complacency is the key.

Bob Towse is head of technical and safety at Building & Engineering Services Association (B&ES), the new name of the HVCA since 1 March 2012.

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