Prevent Legionella in HVAC Systems
Let’s take a look at how to prevent Legionella in your HVAC system. But before we do we must understand what this bacteria is and how it affects building occupants.

Legionnaires’ disease is an infection of the respiratory system. It is a form of atypical pneumonia caused by the Legionella bacteria. While milder than pneumonia, symptoms are similar and include fever, muscle pain, headaches, coughing, and shortness of breath. More severe cases of Legionnaires’ disease may include nausea, vomiting, and diarrhea.

Much of the public views Legionnaires’ disease as a rare illness because it is widely underreported. The majority of cases go undetected and few cases get reported to the media. According to the Centers for Disease Control and Prevention (CDC), there are between 8,000 and 18,000 instances of the disease in the United States each year, yet public awareness remains low.

Legionnaires’ disease has a high cost for building owners in the form of lawsuits and loss of business due to bad press. It also can result in long-term health complications for those who contract it. Understanding the disease and how Legionella bacteria spreads through HVAC systems is important for facilities managers to understand.

How Legionnaires’ Disease Spreads

A person contracts Legionnaires’ disease after exposure to water containing Legionella bacteria. This can happen from a faucet, shower, or hot tub, even decorative fountains and water features. It can also spread throughout buildings in the mist created by cooling towers. Tiny water droplets containing the bacteria get inhaled into the lungs or brought into the lungs by drinking. Facility managers need to have a plan to prevent Legionella from flourishing.

Reducing the Risk of Legionnaires’ Disease

Preventing the spread of Legionella bacteria in building water and air systems is the best defense against Legionnaires’ disease. Any program for reducing the risk of HVAC Legionella should include the following:

  • Assessment
  • Management Plan
  • Education
  • Testing

An expert inspection of facility water and air systems helps identify conditions that will contribute to the growth of Legionella bacteria. A management plan for dealing with water-borne pathogens should be created based on the assessment. Facility managers and outside contractors should receive education on how to identify the bacteria-causing conditions outlined in the plan as well as how to correct them. Regular environmental lab testing and analysis is necessary to detect the presence of Legionella and other harmful bacteria.

Steps to Prevent Legionella

Design, construction, operation, maintenance, and expansion of water systems and air distribution systems is necessary to limit the risk of an outbreak of Legionnaires’ disease. There are things that facilities managers can do with air distribution systems and cooling towers to prevent Legionella contamination while improving the building’s indoor air quality.

Air Distribution Systems

Using steam humidifier units provides better results than cold-water humidifiers. Steam units are less conducive to Legionella because they operate at higher temperatures and generate vapor, not water droplets. Steam humidifiers require periodic descaling as well as draining when not in operation. If steam is not an option, then cold-water humidifiers should be operated with water temperatures of 68°F or below and sourced from a domestic water supply and drain line. Humidifiers should be cleaned and inspected for leaks on a regular schedule. Pipes should also be maintained to prevent contaminated water from entering ducts.

Other tips for limiting the spread of Legionella in air distribution systems:

  • Proper duct design prevents water from accumulating or condensing.
  • Drain lines installed with a trap or air brake prevents HVAC Legionella from being drawn back into the system.
  • Leak-free coils prevent contaminated water from spraying into ducts
  • Condensate drain pans should be kept clean with rusted pans replaced as needed.
  • Air filters should be kept dry, clean, and replaced as necessary.

Cooling Towers

Prevent Legionella Inside Cooling TowersCooling tower control is critical to preventing HVAC Legionella bacteria from spreading. It all comes down to design and engineering. Locating towers, a minimum of 33 feet from outdoor air intakes is safe, however 100 feet is safer. Cooling towers must also be located away from windows, sidewalks, parking lots, or any high traffic areas with opportunities for exposure to building occupants and visitors.

Other tips for limiting the spread of Legionella through cooling towers:

  • Water treatment service plans should make Legionella bacteria control one objective of their treatment plan.
  • Environmental cleaning of cooling towers helps prevent bacteria and corrosion from forming.
  • Remove unused piping where stagnant water can collect and keep piping lengths as short as possible.
  • Check cooling water pH levels and total bacteria count a minimum of twice a week.
  • Install high-efficiency drift eliminators to replace deteriorated ones.

Building Sciences Sample Collection

The Building Sciences Services provided by Pure Air Control Services are an effective way to minimize the development and spread of HVAC Legionella. For example, a Building Health Check evaluates indoor environments based on HVAC zones, while an HVAC Hygiene Assessment gauges how the system impacts IAQ. Samples are collected from water and air sources then sent to EDLab for analysis.

Environmental Diagnostics Laboratory

Legionella Bacteria CultureEDLab is CDC Elite Program and New York State Department of Health Environmental Laboratory Approved Program (#12086) certified for Legionella testing. They utilize NCM Amplification: Non-Culture, Culture, and PCR Molecular methods to identify and quantify Legionella bacteria. PCR Legionella testing provides highly quantitative results from smaller sample volumes within 4-24 hours. Its rapid turnaround time is critical to respond to an emergency outbreak.

Contact Pure Air Control Services with questions about these services or to start testing to prevent Legionella in your HVAC system. Call 1-800-422-7873 today or email us here.