Legionella Safety for Building Occupants

What Causes Legionellosis

Legionella bacteria is increasingly in the news due to small outbreaks in public places, where airborne bacteria contact visitors and building occupants. There are at least 42 strains of legionella, with approximately 19 types that have been observed to cause pneumonia (Legionellosis). The British medical journal The Lancet reported a 219% percent increase in reported cases of Legionellosis infection during 2000-2009, and New York City established regulations that many cities have begun to adopt, because the sources are common in most buildings and facilities. No vaccines can prevent Legionellosis, so prevention is the logical approach.

How Does It Spread?

Legionnaires' disease doesn't spread from person to person. Instead, the bacteria spreads through mist, such as from air-conditioning units, showers, fountains and other devices that cause water to become air borne. Many people exposed to legionella do not develop symptoms. Adults over the age of 50 and people with weak immune systems, chronic lung disease, or heavy tobacco use are most at risk. Often these people are in hospitals, hotels, care centers or indoors for prolonged periods of time where exposure periods are extended.  

Legionella commonly develops in warm, wet environments, usually that contains colonies of other types of bacteria and algae, though it has been found in ice machines as well as hot water systems. Infection occurs after inhalation, so any process that creates fine water droplets or an aerosol such as cooling towers, showers, spas, pools, fountains or water features, or sprinklers) can spread Legionella.

Legionella bacteria are not new, though as urban water systems age and are not properly maintained, the bacteria have become more prevalent in buildings and public facilities. These man-made water sources become a health problem when small droplets of water that contain the bacteria get into the air and people breathe them in. Occasionally, someone breathes in Legionella while they are drinking water and it “goes down the wrong pipe” into the lungs. Legionellosis does not occur until the bacteria reach the lungs.

Legionnaires’ disease is treated with antibiotics, and most people who become infected need care in a hospital but make a full recovery. However, about 1 out of 10 people who get Legionnaires’ disease will die from the infection.

Common Sources of Legionella

Legionella bacteria were first identified in 1976 as the cause of Legionnaires’ disease at a convention in New York City. More recently, rates of contamination and infection increased throughout the United States and around the world.

Not only are there new, unexpected sources of contamination, but also drinking water sources, water systems such as cooling towers, hot water systems, plumbing systems, fountains, spas and systems that allow water to sit for extended periods of time. Grocery store misters have been identified as sources of legionella, as have street cleaning trucks that sprayed water in urban environments.

Common devices such as ice machines have been found to host algae while making and storing ice, which have been found to contain legionella bacteria, and were identified as sources of Legionellosis in hospitals in the U.S. Ideally, chlorine or other disinfectants are able to reach every drop of water, though this is not possible.

What is Being Done to Prevent Legionella

Legionella prevention is the first line of defense, followed by a robust set of monitoring and testing procedures to detect the bacteria early to minimize the risk of more extensive contamination. Building operators should establish a water management program to reduce the risk for Legionnaires’ disease associated with the building water system and devices. This water management program should identify areas or devices in your building where Legionella might grow or spread to people risks can be identified and reduced. Legionella water management programs are now an industry standard for large buildings in the United States.  

The Centers for Disease Control and Prevention (CDC) has developed a Legionella toolkit that includes checklists and resources that follow the ASHRAE 188 standards for Risk Management for Building Water Systems, that was released on June 26, 2015.

Monitoring Programs

Hotel operators, hospitals, cruise lines and many organizations have initiated comprehensive monitoring programs to monitor their facilities for legionella contamination, using trained personnel and 3rd party companies that perform scheduled testing events at their locations.

Bacteria colonies reproduce rapidly, and a well-managed monitoring program will identify locations of bacteria early in development, and will reduce the risk of extensive contamination and risk of infection of employees or visitors. Early detection and a prevention program will help to avoid interruption of business or even a facility closure along with undesirable publicity.

On-site sampling and testing kits are available for use by facility employees to monitor water systems and cooling towers on a schedule, so that prompt action can be taken when a positive result is observed, and set of samples can be sent for confirmation by culture testing at a commercial laboratory.

There are a range of portable testing methods available, that have advantages in terms of timing for some kits that identify total bacteria, while specific legionella analysis requires 2-4 days for results by a laboratory. The bacteria testing market continues to evolve rapidly, with improved tools that quantify legionella bacteria on location being perfected. 

Our company, Hydrotech Solutions, provides testing for total bacteria counts using rapid screening of water systems with results in minutes using Bactiquant®. This technology allows us to validate cleaning methods and to verify cleaning efficacy in near real time.

Samples from locations with results that exceed acceptable levels are submitted to a laboratory for analysis, while actions can be taken at these locations while on site.

HydroTech's Approach for Water Treatment and Conditioning

Disinfection is critical for maintaining low bacteria counts in water systems, and some managed systems like cooling towers and spas use a chlorine program to control bacteria. In potable water systems with water supplied from municipalities, the level of chlorine (ClO2) or similar disinfectants diminishes as the distance from the treatment plant increases. 

On-site disinfection systems are common so that residual levels of disinfectant are present throughout a water distribution and storage system.

Hydrotech Solutions provides HydroFLOW electronic water conditioning devices to supplement chemical disinfection, by applying a constant acoustic frequency that disrupts biofilm and planktonic (free floating) bacteria throughout a water system. Segments of water lines with slow moving or stationary water (dead legs) are difficult for disinfection products to access, though HydroFLOW’s ±150 kHz frequency extends throughout the water system by using the water as the carrier of the signal.

The HydroFLOW also causes scale to cluster into microscopic aragonite (a form of calcite) that cannot attach to piping and equipment. The presence of scale in water systems provides a surface that biofilm can attach and establish colonies that often contain legionella, which is parasitic and obtains nutrients from other bacteria. 

HydroFLOW’s frequency disrupts bacteria and biofilm throughout a water system while controlling scale, which conserves water sourcing and disposal costs, while complementing a water chemistry program.


Legionella come from natural fresh water reservoirs, such as lakes, ponds, and puddles, where they are parasites that rely on a broad range of protozoan species as hosts. The availability of the hosts plays a major role in the reproduction and mass release of highly infectious Legionella forms into environments where they can be spread by airborne water caplets and inhaled by people.

Legionella and other pathogens thrive in man-made aquatic environments where the water temperature is higher than ambient temperature: whirlpool spas, cooling towers, water used for drinking and bathing, water fountains, humidifiers, ice machines, and vegetable misters, etc. Most cases of legionellosis can be traced to using such systems. It is a major concern for health professionals and construction and water systems maintenance workers.

Building operators should develop a water management program to reduce the risk for Legionella growing and spreading within their water system and devices. The CDC toolkit was designed to help people understand which buildings and devices need a Legionella water management program to reduce the risk for Legionnaires’ disease, what makes a good program for a specific building, and how to develop a site-specific program.

Chemical disinfection programs are necessary for water systems, and the use of electronic water conditioning provided by HydroFLOW provide an additional method of support by extending into slow moving and stationary water for disrupting biofilm and bacteria beyond the reach of disinfectants. HydroFLOW is simple to install without cutting into pipes or equipment, and uses 110v, low amperage electricity.


HydroFLOW electronic water conditioning: http://www.hydrotech.solutions/legionella/

ASHRAE 188: Legionellosis: Risk Management for Building Water Systems June 26, 2015. ASHRAE: Atlanta: https://www.cdc.gov/legionella/downloads/toolkit.pdf

Centers for Disease Control and Prevention: Legionella: https://www.cdc.gov/legionella/index.html

Intracellular parasites – Legionella pneumophila: http://www.metapathogen.com/legionella/

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