In this article, Rene Basulto, P.E. provides an engineer’s introduction to Legionnaires Disease. He discusses the way that Legionella bacteria propagates in water systems and how developing industry standards intend to control the spread of the bacteria.
Text Adapted from Original Article, Updated Since Standards were Approved. Original Article Available in PDF in the Details Section of this PageUnlike other water-borne pathogens, Legionnaires’ disease is transmitted by breathing in mist containing Legionella bacteria. This commonly happens in showers, at faucets, in whirlpools, decorative fountains, swimming pools, or via cooling towers in air conditioning systems. The bacteria propagates rapidly in stagnant and warm water, which is why it is so commonly found in untreated potable water systems, air conditioning system components, and hot water systems. CDC data indicates that legionellosis incidence rates nearly tripled during the reporting period of 1997-2012. Year 2012 reported 3,688 cases to the NNDSS showing continually rising incidence rates. Figure 1 - Legionellosis Incidence Trend: line graph presents the incidence per 100,000 population of legionellosis cases in the United States from 1997 to 2012.
Fortunately, legionellosis is preventable through proper maintenance and treatment of the water systems in which Legionella grows, including drinking water systems, and other building systems. For many years, the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE) has provided guidance on preventing legionellosis associated with building water systems. ASHRAE is an industry organization that develops and publishes handbooks, guidelines, and standards for heating, ventilating, and air conditioning system design. Members, who are practicing engineers, in a consensus-based process, develop handbooks, guidelines and standards. ASHRAE Guideline 12 – Minimizing the Risk of Legionellosis Associated with Building Water Systems - provides information and guidance in order to minimize Legionella contamination in building water systems. However, it falls short of establishing a standard of care for the prevention of Legionella contaminations causing outbreaks of the disease. The continually increasing incidences of Legionnaires led ASHRAE and the American National Standards Institute (ANSI) Board of Standards Review (BSR) to develop BSR/ASHRAE 188P. The ANSI BSR is responsible for the approval and withdrawal of American National Standards. The proposed standard was created to help building owners to establish management strategies to prevent legionellosis. The first three versions were titled “Prevention of Legionellosis Associated with Building Water Systems” with a declared purpose “to present practices for the prevention of legionellosis associated with building water systems.” The fourth full publication public review draft presented a new title, “Legionellosis: Risk Management for Building Water Systems,” and a revised purpose “to establish minimum Legionellosis risk management requirements for building water systems.” In an effort to perhaps reduce legal implications and risk, “prevention” was changed to “risk management” in this fourth and final public review draft which closed for comments in November 2014. The Standard was approved by ASHRAE Board of Directors on June 4, 2015 and by ANSI on June 26, 2015, dropped the “P” and became ASHRAE Standard 188, Legionellosis: Risk Management for Building Water Systems. Standard 188 finally establishes the national standard of care for the minimum legionellosis risk management requirements for building water systems. The standard is intended for use by building owners, managers, and those involved in the design, construction, installation, commissioning, operation, maintenance, and service of centralized building water systems and components. The standard requires facilities to implement a water management program that includes a written document with certain components and Legionella control measures. More specifically, a water management program is required if a building or site has any cooling towers, evaporative condensers, hot tubs, ornamental fountains, misters, atomizers, air washers, humidifiers, or any devices that release water droplets into the air. Most importantly, the standard establishes a base line for the minimum requirements for building owners, changing the landscape for litigation of Legionnaires’ disease cases.
Text Adapted from Original Article, Updated Since Standards were Approved. Original Article Available in PDF in the Details Section of this Page