Blog Post

Understanding ASHRAE Standard 188 and Its Application to Healthcare

Healthcare facilities face a heightened obligation to manage waterborne pathogen risks, and Legionella pneumophila sits at the top of that risk profile. ASHRAE Standard 188, titled “Legionellosis: Risk Management for Building Water Systems,” provides the industry-consensus framework for identifying, assessing, and controlling Legionella risk in building water systems. For healthcare administrators and facility managers, understanding this standard is not optional. It is the foundation upon which all modern Legionella testing and water management programs are built.

What ASHRAE 188 Requires

ASHRAE 188 requires building owners and managers to establish a water management program (WMP) for facilities that meet certain risk criteria. Healthcare facilities, including hospitals, long-term care facilities, and outpatient surgical centers, almost universally meet these criteria due to the presence of immunocompromised occupants, complex water systems, and building characteristics that promote Legionella growth.

The standard mandates a systematic approach that includes the following core elements:

• Water management team: A designated, multidisciplinary team responsible for developing, implementing, and maintaining the program.
• Building water system description: A comprehensive description and flow diagram of the facility’s water systems, including potable hot and cold water, cooling towers, decorative fountains, hydrotherapy equipment, and any other system that generates aerosols.
• Hazard analysis: Identification of areas within the water system where conditions favorable to Legionella growth may exist, including dead legs, areas of low flow, inadequate temperature control, and insufficient disinfectant residual.
• Control measures: Implementation of specific interventions to manage identified hazards, such as temperature management, flushing protocols, disinfection procedures, and maintenance schedules.
• Monitoring and validation: Routine monitoring to verify that control measures are functioning as intended, including environmental testing for Legionella.
• Corrective actions: Defined procedures for responding when monitoring reveals that control limits have been exceeded or when a case of healthcare-associated Legionnaires’ disease is identified.

High-Risk Water Systems

ASHRAE 188 applies to all building water systems capable of supporting Legionella growth and transmission. In healthcare settings, the systems of greatest concern include potable hot and cold water distribution systems, cooling towers and evaporative condensers, decorative fountains and water features, hydrotherapy pools and whirlpool spas, and humidification systems. Each of these systems requires its own risk assessment and control strategy within the overall water management program.

CMS Requirements for Legionella Water Management Plans

While ASHRAE 188 provides the technical standard, the Centers for Medicare and Medicaid Services (CMS) provides the regulatory enforcement mechanism that gives the standard its teeth in healthcare settings. Compliance with CMS requirements is directly tied to a facility’s ability to participate in Medicare and Medicaid programs, making non-compliance an existential financial risk.

The CMS Memorandum: S&C 17-30

In June 2017, CMS issued Survey and Certification memorandum S&C 17-30-HO, which established the requirement for all Medicare-certified healthcare facilities to maintain water management programs that reduce the risk of Legionella and other waterborne pathogens. The memo explicitly references ASHRAE 188 and CDC guidance as the basis for compliant programs. This applies to hospitals, critical access hospitals, and long-term care facilities.

What Surveyors Look For

During CMS surveys, accreditation body inspections, and state health department reviews, surveyors evaluate whether a facility has implemented a comprehensive water management program. Specific areas of focus include:

• Evidence of a functioning water management team with documented meetings and activities.
• A current, facility-specific water management plan that addresses all relevant water systems.
• Documentation of routine monitoring activities, including temperature checks, disinfectant residual measurements, and environmental Legionella testing results.
• Records of corrective actions taken in response to monitoring exceedances or positive Legionella results.
• Evidence of staff training on the water management program.
• Integration of the water management program with the facility’s infection prevention and control program.

Consequences of Non-Compliance

Facilities found to be non-compliant with CMS water management requirements may receive deficiency citations, which can escalate to immediate jeopardy findings if the deficiency poses a serious risk to patient safety. Repeated or severe deficiencies can result in denial of payment for new admissions, civil monetary penalties, and ultimately termination from the Medicare and Medicaid programs. Beyond regulatory consequences, a Legionnaires’ disease outbreak linked to a healthcare facility carries catastrophic reputational damage and significant legal liability.

How Often Should Healthcare Facilities Test for Legionella?

Environmental testing for Legionella is a critical component of any water management program, but the question of testing frequency requires a nuanced, risk-based approach. Understanding legionella testing requirements for healthcare settings means going beyond minimum compliance to establish a testing cadence that provides meaningful surveillance data.

CDC Recommendations

The CDC recommends that healthcare facilities with populations at increased risk for Legionnaires’ disease, which includes virtually all hospitals and long-term care facilities, conduct routine environmental testing for Legionella as part of their water management programs. Testing provides baseline data on the presence and concentration of Legionella in building water systems and serves as a validation tool for control measures.

Quarterly Baseline Testing

Industry best practice, supported by both CDC guidance and infection prevention organizations, is to conduct environmental Legionella testing on a quarterly basis at minimum. Quarterly testing captures seasonal variations in Legionella levels that may correlate with changes in water temperature, water usage patterns, or municipal water supply characteristics. A robust quarterly testing plan should include samples from representative locations throughout the water system, including distal outlets (faucets and showerheads), hot water return lines, storage tanks, and cooling tower basins.

Event-Triggered Testing

Beyond routine quarterly sampling, additional testing should be triggered by specific events or conditions, including:

• Construction or renovation: Any construction activity that disrupts the building water system, including pipe modifications, water shutoffs, or pressure changes, should trigger follow-up testing.
• Water system changes: Installation of new equipment, changes in disinfection methods, or modifications to temperature setpoints warrant verification testing.
• Clinical cases: Any suspected or confirmed case of healthcare-associated Legionnaires’ disease requires immediate environmental sampling to identify potential sources.
• Water quality complaints: Reports of discolored water, unusual odors, or temperature irregularities should prompt targeted testing.
• Extended low-use periods: Prolonged periods of reduced water use, such as wing closures or seasonal census decreases, create conditions favorable to Legionella growth and should be followed by testing before returning systems to full use.

Post-Remediation Verification

When elevated Legionella levels are detected, remediation actions such as thermal disinfection, hyperchlorination, or supplemental disinfection system installation must be followed by verification testing. Post-remediation samples should be collected after an appropriate waiting period, typically two to four weeks after treatment, to allow any surviving organisms to reach detectable levels. Multiple rounds of negative results are generally required before a system is considered cleared.

Culture vs. PCR: When to Use Which

Two primary analytical methods are available for environmental Legionella testing: culture and quantitative polymerase chain reaction (qPCR). Each has distinct advantages depending on the testing objective:

• Culture method: Culture remains the gold standard for environmental Legionella testing. It detects only viable (living) organisms, provides species and serogroup identification, and allows for comparison with clinical isolates in outbreak investigations. Culture results typically take 7 to 14 days. For routine monitoring and regulatory compliance, culture is the preferred method.
• qPCR method: qPCR provides rapid results, often within 24 to 48 hours, by detecting Legionella DNA. It is highly sensitive and can be valuable for screening, rapid risk assessment, and post-remediation monitoring. However, qPCR detects both viable and non-viable organisms, which can complicate interpretation after disinfection treatments. It does not replace culture for definitive identification.

Many healthcare facilities use both methods as part of a comprehensive testing strategy, employing qPCR for rapid screening and culture for definitive identification and regulatory documentation.

Choosing the Right Lab for Legionella Culture Testing

The accuracy and reliability of your Legionella testing program depend directly on the laboratory performing the analysis. Not all labs are qualified to perform environmental Legionella culture, and selecting the wrong lab can undermine your entire water management program.

The Importance of CDC ELITE Certification

The CDC’s Environmental Legionella Isolation Techniques Evaluation (ELITE) program is the nationally recognized proficiency testing program for laboratories performing environmental Legionella culture. CDC ELITE certified laboratories have demonstrated their ability to accurately isolate and identify Legionella from environmental water samples through rigorous proficiency testing. When selecting a laboratory for legionella testing requirements in healthcare, CDC ELITE certification should be considered a non-negotiable minimum qualification.

Culture Method vs. qPCR: Practical Considerations

While both methods have their place, your laboratory partner should offer expertise in both culture and qPCR methods and should be able to advise you on the appropriate method for each testing scenario. Key practical considerations include:

• Turnaround time: Culture results require 7 to 14 days, while qPCR can deliver results in 24 to 48 hours. For routine monitoring, culture turnaround times are generally acceptable. For emergency situations or outbreak investigations, qPCR provides the rapid results needed for immediate decision-making.
• Serotyping capability: In outbreak situations, the ability to identify Legionella to the serogroup level and perform molecular typing is essential for source attribution. Ensure your laboratory can provide these advanced characterization services.
• Sample volume capacity: Healthcare facilities with large or complex water systems may need to submit dozens of samples simultaneously. Confirm that your laboratory has the capacity to handle your sample volume without delays.

What to Look for in a Lab Partner

Beyond technical qualifications, evaluate potential laboratory partners on the following criteria:

• Accreditation: Look for both CDC ELITE certification for Legionella culture and ISO 17025 accreditation for overall laboratory quality management.
• Experience: Laboratories with decades of experience in environmental Legionella testing bring institutional knowledge that translates directly into more reliable results and better technical support.
• Consultation support: The best laboratory partners do more than process samples. They provide guidance on sampling plans, help interpret results, and offer recommendations for corrective actions.
• Emergency response: Legionella situations can escalate rapidly. Your laboratory partner should offer emergency response capabilities, including expedited sample processing and rapid reporting for urgent situations.
• Reporting clarity: Test results should be delivered in clear, well-organized reports that facilitate decision-making by your water management team and satisfy regulatory documentation requirements.

Why Healthcare Facilities Choose AATLS

AATLS (American Analytical Testing Laboratory Services) brings more than 30 years of experience in environmental Legionella testing to healthcare facilities nationwide. As a CDC ELITE certified and ISO 17025 accredited laboratory based in Tucson, Arizona, AATLS combines technical excellence with the responsive service that healthcare facilities require. Our team understands the regulatory pressures facing healthcare administrators and provides the documentation, consultation, and rapid turnaround that effective water management programs demand.