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Blog: 7 Ways to Protect Building Occupants from Legionnaires’ Disease

New York City’s recent outbreak of Legionnaires’ disease has given property managers everywhere reason for concern. Affecting 121 people and killing 12, this tragic occurrence highlights just how lethal the legionella organism can be—and how prevalent. 

The Legionella pneumophila bacterium is naturally present in many water sources. When inhaled in water droplets or mist, it can lead to a serious type of pneumonia known as Legionnaires’ disease, or legionellosis. Between 8,000 and 18,000 people are hospitalized for legionellosis each year in the U.S., and the annual count appears to be climbing. 

According to a report from the Centers for Disease Control and Prevention (CDC), incidences of legionellosis grew by more than 192 percent between 2000 and 2009. Despite its widespread presence in lakes and streams, virtually all confirmed cases of Legionnaires’ disease have been traced to man-made water sources. 

Cooling towers, such as those implicated in the New York City outbreak, are prime candidates for legionella growth. However, they are not actually the most common sources. A 1998 study found that hot water heaters had almost twice the rate of legionella contamination as cooling towers. Hot tubs are also common places for the organism to thrive—but don’t overlook cold water sources. According to a CDC spokesperson, “Potable water is another common source people may not think about. [And] many people might be surprised that decorative fountains can harbor legionella.” 

Sound like a major liability? You’re absolutely right. Here are a few ways you can protect your building’s occupants from Legionnaires’ disease—and protect yourself from lawsuits. 

1. Review all HVAC and plumbing systems. Legionella thrives in stagnant water between 77°F and 113°F. It is a good idea to inspect any system or piece of equipment you have that may contain such a water source. Look for dead legs, storage tanks and other low-flow conditions such as stagnant water remaining in a seldom-used pump. If possible, redesign for the elimination of these hazards. Create a plan for regular inspection and maintenance of those areas that can’t be avoided.

2. Test for legionella. If you have found one or more conditions on your property that you think may harbor legionella, you might want to consider testing for the organism. A routine testing and monitoring program is recommended for buildings that house at-risk occupants such as very young children and the elderly. 

3. Clean and disinfect your systems and equipment. Slime, scale and sediment harbor legionella growth. Many people are not aware that the reproductive cycle of these bacteria occurs within microorganisms that live in stagnant water conditions. Thus, keeping your equipment clean of all micro-flora will go a long way towards reducing the risk of a Legionnaires’ outbreak in your building. 

4. Set your water heaters to the proper temperature. Domestic hot water temperatures that are set too low will create ideal conditions for Legionnaires’ disease. Set your water heater for 140°F at the tank, and no less than 122°F at the tap. 

5. Insulate your hot water pipes. Be aware that hot water temperatures can drop significantly between the tank and the tap. Insulating your hot water lines can help ensure that your hot water stays at a temperature that will inhibit bacterial growth.  

6. Install tempering valves where appropriate. Raising hot water temperatures for Legionnaires’ prevention can increase the risk of scalding, especially in buildings that house small children. Installing a tempering—or mixing—valve at the tap will mix enough cold water in at the point of use to prevent burns. 

7. Budget for adequate ongoing cleaning maintenance. “Right now a lot of maintenance budgets are being cut,” says Ray Field, director of liquid solutions at Goodway Technologies. “There’s a high correlation between maintenance budget and legionella outbreak. If you’re not doing preventative maintenance on a consistent basis, you raise your probability of contamination.” The new Legionellosis Risk Standard developed by ASHRAE is an excellent resource for property managers interested in legionellosis prevention. 

While Legionnaires’ disease is a serious issue, it’s no reason to panic. Many cases of legionellosis actually go undetected, and most buildings that test positive never result in disease. Following these best practices for legionellosis prevention will help ensure that you never experience a problem. 


Anne Michelsen is a freelance writer with expertise in areas including construction, small business management and sustainability (www.thegreeninkwell.com).

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