ASHRAE Calls for Action on Legionella Risk in Buildings

Recent Legionnaires' disease outbreaks in New York City and Ohio have reignited concerns around water safety in commercial and institutional facilities. With aging infrastructure, fluctuating building occupancy, and increasingly frequent extreme weather events, the conditions are ripe for Legionella bacteria to spread within building water systems.

Heavy rainfall and flooding events not only damage infrastructure—they also disrupt normal water flow and create stagnant conditions that support bacterial growth. Biofilms dislodged during storms can lead to widespread contamination, particularly in older systems with limited capacity for real-time monitoring. For facilities in flood-prone regions, or those relying on dated municipal water networks, the risks are even greater.

In response, facilities need to move beyond reactive fixes. Emergency protocols are important, but prevention starts with comprehensive, site-specific water management strategies that account for environmental and infrastructure vulnerabilities.

 Updated Industry Guidance Targets Risk Management

To help the building industry address these challenges, ASHRAE has emphasized two key documents that provide a structured approach to Legionella prevention.

ANSI/ASHRAE Standard 188-2021 lays out legally enforceable requirements for managing Legionella risk throughout a building’s lifecycle. Its integration into building codes helps align facility operations with public health regulations.

Meanwhile, ASHRAE Guideline 12-2023 offers actionable guidance on how to reduce Legionella growth across various systems—from potable water and cooling towers to fountains and spas. It focuses on system-specific risks and includes practical details on treatment methods, monitoring strategies, and worker safety practices.

By implementing these standards, building operators can reduce potential liability, align with public health expectations, and strengthen their operational resilience. Standard 188 provides the regulatory framework; Guideline 12 fills in the operational details.

As ASHRAE President Bill McQuade put it, safe, healthy buildings depend on proactive, preventive water system management. “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.”