Most likely you have read the articles about Legionnaires’ outbreaks, including several recent cases throughout the country. This is not a new issue, however, it begs the question – How do we eradicate this growing problem?
WHAT IS IT?
Legionellosis (Legionnaires’ Disease and Pontiac Fever) is a respiratory disease that can cause a lung infection, presenting with fever and flu-like symptoms. The disease can be contracted when an individual breathes in small droplets of water in air that contains Legionella. According to the Centers for Disease Control (CDC), the number of cases reported since 2000 has increased more than five times. Because the disease can be underdiagnosed, the actual number may be higher.
WHERE DOES IT ORIGINATE?
Building water systems are the most common culprit, especially in man-made water systems typically found in large facilities with potable water, hot tubs, hot water tanks and heaters, plumbing systems, cooling towers, and decorative water features.
Warm water, such as the temperature found in a hot tub, can provide the ideal breeding environment for Legionella to multiply. A Building Owner / Manager must establish and follow a Water Management Program to monitor and control chemical levels, maintain manufacturers’ cleaning guidelines, and conduct regular maintenance of all water-related systems.
HOW CAN ENGINEERING HELP TO COMBAT THE ISSUE?
Mechanical engineers should pay attention to ASHRAE Guideline 12-2000 Minimizing The Risk of Legionellosis Associated with Building Water Systems, and ASHRAE Standard 188: Legionellosis: Risk Management for Building Water Systems.
Building cooling towers are a high-risk area. Legionella bacteria grows best between water temperatures of 72 – 113 degrees Fahrenheit, thus creating a perfect breeding ground. Major maintenance programs should be established during the design process. Cooling towers should be treated with a dual biocide that uses both oxidizing and non-oxidizing biocide whenever possible. According to OSHA, cooling towers and evaporative condensers should be inspected and cleaned twice a year, under the supervision of a technician trained in Legionella remediation. Due to potential Legionella bacteria existing in cooling towers and the vapor mist that cooling towers emit, they should not be installed close to building air intake or windows that may be opened.
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