these valves are cleaned regularly and functional.

Legionella in cooling towers ‘Cooling Tower’ is an umbrella term for a variety of equipment that utilises evaporative heat rejection for cooling. Depending on the design of the specific equipment, its location on a site, and the seasonal conditions present, these systems can be a perfect vehicle for growing and spreading Legionella. If they are not adequately cleaned and

disinfected, they may have reservoirs of warm water growing bacteria. That water is used to absorb heat from HVAC systems and that heat is ejected into the atmosphere through evaporation. This process can cause clouds of mist that can make their way into outside air intakes of buildings, directly into the lungs of passersby etc. Cooling towers have been linked to

many Legionella outbreaks over the years – this is not late-breaking news. As most of us in the industry are aware, improperly-maintained cooling towers were blamed for multiple outbreaks in recent years – including 2018. The US Centers for Disease Control, the EPA, and ASHRAE are addressing this issue and have provided guidelines and recommendations for cooling tower design, siting, and operation. Newer towers with high-efficiency drift

eliminators, automated controls for water temperature maintenance and blowdown, as well as microbial control systems using filtration, biocides, and copper/silver ionisation have resulted in great progress towards eliminating this threat. However, diligent maintenance is most important. Any facility’s water management plan must include plans for operating, maintaining, shut down, startup, and testing water quality in cooling tower systems.

Legionella in humidifiers, decorative fountains, and whirlpool tubs These categories are often included in lists of Legionella-harboring equipment and, indeed, all three have been linked to outbreaks. However, in most healthcare

Hospital water systems can be a source of Legionella.

settings, point of use humidifiers are simply not allowed. In healthcare, steam humidification must be built into the building HVAC systems wherever humidification is required. Steam does not carry Legionella. Meanwhile, decorative fountains and whirlpool therapy tubs that generate water vapour have fallen out of (popular) use in new hospital designs due to the widely known risk of hospital-acquired infections associated with them.

ASHRAE Standard 188: Legionellosis: Risk Management for Building Water Systems ASHRAE Standard 188 establishes minimum Legionellosis risk management requirements for building water systems. The standard includes Normative Annex A: Health Care Facilities which is geared more towards hospitals’ meeting the intent of the CMS conditions of participation. The standard requires that a Water Management Team (WMT) be

To further add potential risk, many fixtures may be infrequently-used and may be located at the end of a long, uncirculated branch pipe run. ‘Hot’ water in piping serving those fixtures will cool off and may spend much of the day in the perfect temperature range for Legionella growth


assembled including: hospital executive leadership, facility management, and infection prevention. The WMT may also include representatives from nursing management, occupational and environmental safety, and other departments. as the facility sees fit. The WMT’s job is to create a Water Management Plan (WMP), meet regularly to ensure the plan is properly implemented and maintained, and to provide direction when potential epidemiological issues arise.

Water management plan The WMT will likely need to enlist the aid of design engineers, water treatment specialists, infection preventionists, and others with waterborne pathogen expertise to help develop the plan. The plan needs to include a map of the facility water systems including sources, equipment, use points, and areas where at-risk patients may be exposed to aerosolised water. The WMT needs to identify locations in the system map where conditions are most likely to result in pathogen growth and exposure to at-risk patients. These locations are referred to as ‘control locations’. Standard 188 includes many more details on what should be included in the water system map and how to identify the risks. Once the control locations are

established, the team must decide on acceptable control limits for each location. These may include a variety of parameters such as water temperature, disinfectant concentrations, pathogen concentrations, etc. The WMT establishes how the control locations are tested, the testing schedule, and a plan of action if the control limits are exceeded. Since some pathogens are common

at low levels and do not pose a significant risk, the control limits will help ensure the WMT does not overreact to test results that do not pose a significant risk. Through the ongoing process of monitoring the control points, the facility will develop a baseline from which deviations will be easier to notice and interpret. When control limits are exceeded, the team may implement a one-time intervention such as isolating and disinfecting a single faucet or small area of piping. They may instead implement a regular

maintenance activity such as on-site supplemental disinfection, regular flushing of sections of the piping system, or adding point-of-use filters to problem fixtures. The process of developing the WMP and monitoring the control points will also almost certainly inform planning of regular maintenance as problem areas are identified. Ultimately, the health of facility water systems should improve, and hospital staff can focus on healing. IFHE



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