Legionella Threat from Air Humidifiers: A Hidden Danger in Industrial Settings

Air humidifiers play a crucial role in maintaining optimal environmental conditions in production and storage facilities as well as in public and commercial buildings. Examples of such facilities range from the production of diapers, MedTech and pharma production, wood processing, electronics and chip manufacturing, food production and storage facilities, up to data centers and also include hospitality, hospitals and office buildings. Air humidifiers add moisture to the air and therefore help control humidity levels, which is vital for product and process quality, for the operation of production equipment and for the wellbeing of employees, guests and patients.

However, air humidifiers also pose a hidden danger: the threat of Legionella transmission. Legionella are dangerous bacteria that can proliferate in water systems and become aerosolized in air humidifiers. Legionella can cause a deadly form of pneumonia, called Legionellosis or Legionnaires’ disease, when inhaled by humans. Health authorities around the world have recognized Legionella and Legionellosis as a substantial threat and health burden to society. In this blog post, we will explore the Legionella threat from air humidifiers in industrial settings, its potential consequences, and ways to mitigate this risk.

Understanding Legionella Risk

Legionella are bacteria known for causing a severe and potentially fatal respiratory illness called Legionellosis, also known as Legionnaires' disease. The bacterium thrives in water environments, especially those with temperatures ranging from 25°C to 42°C. Air humidifiers not only provide ideal conditions for Legionella growth but also maximize the risk of Legionella transmission by spreading potentially contaminated water in the form of aerosols.

In industrial settings, the use of air humidifiers is widespread. Typical settings include manufacturing facilities, data centers, and storage halls, where humidity control is necessary for several reasons:

  • Product Quality: In manufacturing facilities, proper humidity control is vital for product quality, particularly in industries like pharmaceuticals, textiles, and food processing.
  • Equipment Protection: Sensitive equipment, such as servers and electronics, requires optimal humidity levels to prevent damage from static electricity and moisture-related issues.
  • Worker Comfort and Productivity: Maintaining appropriate humidity levels ensures worker comfort, which can boost productivity and overall job satisfaction.

Despite these benefits, the Legionella threat should not be underestimated. When water contaminated with Legionella is dispersed into the air through humidifiers, the bacteria can be inhaled by workers, potentially leading to Legionellosis.

Mitigating the Legionella Threat

The consequences of contamination of air humification system with Legionella can be severe, both in terms of health and operations. An outbreak of Legionellosis within an industrial facility can lead to operational disruptions, including worker illnesses, potential lawsuits, and reputational damage. Legionellosis often presents itself with symptoms similar to pneumonia, including fever, cough, and difficulty of breathing. In severe cases, it is lethal. Individuals with weakened immune systems or underlying health conditions are particularly vulnerable. Many countries have strict regulations and guidelines for controlling Legionella in water systems. Failing to meet these standards can result in legal consequences and fines [2].

To protect both human health and industrial operations, it is crucial to take proactive measures to mitigate the Legionella threat from air humidifiers.

  • Water Quality: The source of water used in humidifiers should be monitored and treated as necessary to reduce the risk of Legionella contamination. The use of filtered and treated water should be considered to ensure its quality.
  • Regular Maintenance: Frequent inspection and maintenance of air humidifiers are essential. This includes cleaning, disinfection, and descaling to prevent the buildup of biofilm where Legionella can thrive. Manufacturers often provide guidelines for maintaining their equipment [1].
  • Temperature Control: Maintaining the water temperature outside the Legionella growth range is an effective strategy. If possible, using temperature-controlled humidifiers can keep the water below 25°C or above 42°C. [3] 
  • Air and Waterborne Bacteria Monitoring: Implement regular testing for Legionella in both air and water samples. Early detection can help prevent outbreaks and allow for timely intervention. The detection of Legionella in aerosols is now possible with the rqmicro.COUNT. Read more.

Legionella Control in Industrial Settings with rqmicro.COUNT

Humidifiers are essential for maintaining optimal environmental conditions in industrial and commercial settings, but they also pose a Legionella threat. Existing testing methods for Legionella are subject to significant delays, making it impossible to respond to potential outbreaks in a timely manner. 

Fortunately, rqmicro.COUNT is transforming Legionella testing. This innovative solution allows industrial facilities to conduct on-site testing that provides results in as little as two hours. Its flow cytometric technology provides accurate and reliable quantification of live and dead Legionella in water samples, allowing for fast and effective water treatment measures to avoid outbreaks of disease. rqmicro.COUNT is changing the game, providing a safer and more efficient approach to Legionella control in industrial settings.


[1] Scott T.,Condair website. Legionnaires' disease & humidifiers - what you need to know

[2] The Health and Safety Executive (HSE). Firm fined following outbreak of Legionnaires’ disease. June 2023.

[3] Centers for Disease Control and Prevention (CDC). Controlling Legionella in Other Devices. February, 2021.

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