At Risk: Any person who is more susceptible than the general population to developing legionellosis because of age, health, medication, occupation, or smoking.

Control: To manage the conditions of an operation in order to maintain compliance with established criteria (water safety term).

Control Limit: The maximum, minimum, or range of values of a chemical or physical parameter associated with a control measure must be monitored and maintained to reduce the occurrence of a hazardous condition (i.e. Legionella).

Control Location: A point in which a physical, mechanical, operational, or chemical control measure is required to manage the occurrence of a hazardous condition (i.e. the growth of Legionella) [water safety term].

Control Measure: A method or procedure used to maintain the physical or chemical conditions of water to within control limits (water safety term).

Disinfection: A process of killing or inactivating pathogens.

Corrective Action: An action taken if monitoring indicates that control measures are outside established control limits in response to plan validation and event-triggered risk (water safety term).

Hazard: A biological, chemical, or physical agent that has the potential to cause illness or injury in the absence of its control.

Hazard Assessment: ASHRAE 188 defines a hazardous condition as “a condition that contributes to the potential for harmful exposure to Legionella.” The CDC Toolkit defines a hazardous condition as “anything that, if not controlled, contributes to the growth and spread of Legionella to a person.” In this plan, the hazard assessments look at the conditions that can exist at the water processing points and components that lead to the growth and spread of Legionella in the water system.

Legionella: The genus Legionella is a pathogenic group of gram-negative bacterium that includes the species L. pneumophila, which causes approximately 90% Legionnaires’ disease cases. Legionella is common in many natural and manmade aquatic environments, with 60 species and 70 serogroups identified.

Legionellosis: Generic term used to describe a collection of infections that emerged in the second half of the 20th century and that are caused by Legionella pneumophila and related bacteria. The severity of legionellosis varies from mild febrile illness (Pontiac fever) to a potentially fatal form of pneumonia (Legionnaires’ disease) that can affect anyone, but principally affects those who are susceptible due to age, illness, immunosuppression and other risk factors, such as smoking.

Legionnaires’ disease: The most severe and common form of pneumonia caused by Legionella. Symptoms are nonspecific; however, the disease has a rapid onset and can be fatal (see Legionellosis).

Monitoring: Maintaining regular surveillance through observation and measurement. Used to demonstrate that the system is operating within the prescribed control limits.

Monitoring Procedures: a set of procedures describing the monitoring.

Process Flow Diagram: ASHRAE 188 requires describing potable and non-potable water systems associated with legionellosis risk in sufficient detail to enable control location identification, analysis, and to allow for management of this risk. The process flow diagram in addition to a written system description, identifies the major water processes or components that could impact the opportunity for Legionella to grow or spread in the water system.

Risk: The possibility that due to a certain hazard there will be a negative effect of a certain magnitude.

Risk Characterization: A process to evaluate the probability of the risk occurring and the magnitude of the effect.

Validation: Water safety term, as defined in ASHRAE 188, initial and ongoing confirmation that the plan, when implemented as designed, effectively controls the hazard (i.e. growth of Legionella). Validation points are monitoring locations where the plan effectiveness can be determined. Validation is accomplished in this plan through environmental sampling for Legionella.

Verification: Water safety term, as defined in ASHRAE 188 Verification is confirmation through periodic review that the plan is being implemented as designed. Verification is accomplished in this plan through routine monitoring of plan documentation of control limits, control measures, and corrective actions.

Water Safety and Management Plan: ASHRAE 188 and other Legionella risk management approaches can reduce the risk from exposure to Legionella in building water systems. Developing and implementing a WSMP is one recommended approach. A WSMP identifies control locations, operating goals, control limits, validation points, and corrective actions for each water system subject to Standard 188.

Program Team: A group of individuals that reviews the monitoring results and assesses the effectiveness of control measures. The program team also makes decisions regarding additions or changes to the WSMP. As described in ASHRAE 188, the team shall have, “knowledge of the building water system design and water management as it relates to legionellosis.” This requires both internal and external resources and expertise.