Legionella Exposure Control plan

Legionellosis is a respiratory disease caused by inhalation of Legionella bacteria. Exposure can lead to a serious lung infection, termed Legionaires' disease, or mild infections similar to the flu. Lung infections related to bacterial exposure are treated with antibiotics. Most affected individuals will require medical care but make a full recovery. However, about 1 out of 10 people who get Legionaires' disease will die from the infection. More importantly, CDC investigations show 90% of all outbreaks were caused by problems which are preventable with more effective water management plans

Legionella bacteria are widely distributed in water systems. They tend to grow in biofilms or slime and are not completely eradicated by chlorination used to purify domestic water systems. Low and even non-detectable levels of the the bacteria can colonize a water source and grow to high concentrations under the right conditions, including the following

  • Water stagnation: Encourages biofilm growth and reduces temperature and levels of disinfectant. Common issues that contribute to water stagnation include renovations that lead to 'dead legs' and reduced building occupancy.
  • Water temperature fluctuations (The optimal growth temperature for Legionella is 68-122degrees F)
  • Water pH between 5.0 - 8.5
  • The presence of scale and sediment in water the promotes bacterial growth
  • Other micro-organisms which can supply Legionella with essential nutrients for growth including algae and other bacteria, commonly referred to as 'biofilm'

When one or more of these conditions are met, there is a risk for Legionella to be present in a water system. Exposure to the bacteria becomes a hazard when it grows and spreads in human-made water systems such as showers and faucets; cooling towers; hot tubs; decorative fountains; hot water tanks; and large building plumbing systems.

There are no vaccinations to prevent legionellosis. Instead, the key to preventing exposure is ensuring water systems in buildings are properly maintained in order to reduce the risk of Legionella growing and spreading.

  • Cooling towers should be on a preventative maintenance program to provide regular cleaning; disinfection; and corrosion prevention
  • Potable and emergency water systems should be chlorinated and temperatures maintained to reduce bacterial growth. In health care and other high risk facilities, hot water should be stored at 140 degrees F and circulated at a minimum of 124 degrees F. All other facilities should ensure hot water is maintained above 120 degrees F. Additionally, hot water tanks should be inspected and cleaned regularly to reduce sediment, scaling and corrosion.
  • Hot tubs must be continually disinfected to reduce growth conditions for bacteria. Water and air jets should be set to run no longer than 15-20 minutes and users should be encourages to spend no more than 15 minutes in a hot tub; and should practice good personal hygiene prior to entering to maintain organic materials at a low level.
  • Decorative water features should use minimum amounts of piping; have drains located in the system to allow for complete drainage and cleaning; cleaned and disinfected regularly; use only water that has been treated by a municipal water treatment system; and maintain water temperature below 70 degrees F.
  • Humidifiers and air misters should use only water that has been treated by a municipal water treatment system; be cleaned and disinfected regularly; and maintain water temperatures below 70 degrees F.
In order to properly manage the risk of Legionella growth and exposure, a Water Management Plan should be implemented.

It is important to continually review Water Management Plans to ensure building changes do not affect the likelihood of Legionella growth

Click on the buttons below for useful links related to the OSU Legionella Exposure Control Plan

To access the online training module for this Safety Program visit:

For questions concerning the Legionella Exposure Control Plan feel free to contact OSU EHS at 614-292-1284 or visit:

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