ASHRAE shares resources to address Legionella risk

ATLANTA, Georgia, United States, 8 August 2025: The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) has expressed its growing concern surrounding the recent clusters of Legionnaires’ disease cases, specifically in New York City and parts of Ohio. Making the announcement through a Press Release, the society emphasised its role in providing guidance on Legionellosis risk management to support public health and building safety.

According to ASHRAE, Legionnaires’ disease, a serious form of pneumonia caused by Legionella bacteria, is most commonly associated with water systems where water is not adequately monitored or treated. ASHRAE said that following periods of heavy rains and flooding, there is an increased risk of the disease due to potential contamination of water sources and disruptions to water systems. Flooding can mobilise Legionella bacteria-rich biofilms in water systems, leading to higher bacterial loads and potential colonisation of the built environment, ASHRAE said. While the disease has been known for decades, recent outbreaks have underscored the importance of consistent, comprehensive water management practices in facilities of all sizes and types, ASHRAE added.

To assist building professionals, public health officials and facility managers in managing this risk ASHRAE said it offers two key resources:

● ANSI/ASHRAE Standard 188-2021, Legionellosis: Risk Management for Building Water Systems, which establishes minimum risk management requirements for the design, construction, commissioning, operation, maintenance, repair and expansion of building water systems. ASHRAE said the resource is written in enforceable language, the standard is designed to facilitate integration into building codes and public health regulations.

● ASHRAE Guideline 12-2023, Managing the Risk of Legionellosis Associated with Building Water Systems, which serves as a companion to Standard 188, offering practical, system-specific guidance on reducing the risk of Legionella growth and transmission. ASHRAE said the guideline addresses common sources of exposure, including potable water systems, decorative fountains, whirlpool spas, cooling towers and humidifiers. Additional sections cover US water treatment regulations related to incoming water quality, Legionella monitoring and personal protective equipment (PPE) considerations.

Bill McQuade, President, ASHRAE, said: “Healthy buildings depend on comprehensive water management strategies. As concerns about Indoor Environmental Quality and public health continue to grow, it’s vital that building owners and operators have access to proven, science-based resources like ASHRAE Standard 188 and Guideline 12. These tools are designed to support safer environments through practical and preventive measures related to water quality and legionella risk mitigation.”

ASHRAE said that the recent outbreaks highlight the ongoing need for vigilance in managing both public water distribution networks and building water systems, especially as many buildings operate under varying occupancy levels and as water utility infrastructure is ageing. ASHRAE said the guidance offers design teams, building managers and health officials a structured approach to mitigating risk and protecting occupants.

McQuade said: “Our Society remains focused on supporting healthy buildings through better air, better water and better system design. We encourage the building community to take advantage of the resources we’ve developed to help prevent future outbreaks.”