Poor workplace indoor air quality has been tied to numerous health problems. These problems include occupational asthma, bronchitis, lung cancer, and allergies which can negatively affect employees’ productivity, cognition, and work performance.

But have you ever heard of Legionnaires’ disease?

What is Legionnaires’ disease? 

Legionnaires’ disease is a form of pneumonia, but a more severe one. It is caused by Legionella bacteria which can be found in wet and damp environments.

According to the Canadian Center for Occupational Health and Safety (CCOHS), the term “Legionnaires’ disease” was first used in 1976 after an outbreak of a type of pneumonia affected many delegates attending the American Legion Convention in Pennsylvania. The bacteria that was responsible for the outbreak was then isolated and named Legionella pneumophila.

Legionella pneumophila belongs to the genus Legionella. While there are many Legionella species known to cause the disease, Legionella pneumophila is responsible for 85 to 90% of its cases. Legionella species can survive for several months in wet or damp environments. They can grow and multiply in the presence of algae and organic matter.

Signs and Symptoms 

Legionnaires’ disease usually develops 2 to 10 days after being exposed to the bacteria. The disease commonly begins with the following signs and symptoms:

  • Muscle pain
  • Headache
  • Uneasiness

After a couple of days, symptoms may develop, this can include:

  • High fever (40-40.5°C or 104-105°F)
  • Nausea
  • Vomiting
  • Diarrhea
  • Dry cough
  • Chest pain
  • Difficulty breathing
  • Hallucinations and loss of memory

The groups of people who are at a higher risk of infection include:

  • People over 50 years of age
  • Smokers and heavy drinkers
  • People with heart disease, chronic respiratory or kidney disease
  • Anyone with a weak immune system

Can Legionella pneumophila spread in your workplace? 

Majority of modern day workplaces are at risk of exposure to Legionella since almost all businesses and infrastructure have installed hot and cold water, and air conditioning systems to ensure cleanliness and proper hand hygiene. The European Agency for Safety and Health as Work or the EU-OSHA reported that many equipment and work environments are ideal locations for Legionella pneumophila to grow.

The below are certain occupations that are exposed to an increased legionella risk:

  • Workers who clean and maintain cooling towers
  • Air conditioning engineers
  • Plumbers
  • Spa pool cleaners
  • Hotel and cruise ship workers
  • Laboratory analysts

The Legionella bacteria grows and multiplies in wet, damp, and slimy areas including the water inside poorly maintained HVAC systems. When Legionnaire is present, it can be spread into the air through aerosols or small droplets when the system is switched on. This can be inhaled and can enter into the lungs especially when there is no adequate air flow in the workplace.

The bacteria flourish in temperatures ranging from 90 to 105 degrees Fahrenheit. This is the reason why it is crucial to monitor workplace indoor air quality. By monitoring and managing workplace indoor air quality, all the factors that contribute to Legionnela growth, including humidity and temperature, can be controlled and can be maintained strictly in their optimal state.

Another way to prevent Legionella growth is through routine air duct cleaning. Through thorough duct cleaning, dirt, pollen, mold, and aerosols containing the legionella bacteria will be removed. Additionally, this will keep your system in great working condition.

Ensuring proper ventilation is also an ideal step to mitigate Legionella risk. Ventilation is the act of controlling indoor air quality by  introducing outdoor air into an enclosed space.  Proper ventilation reduces legionella contamination by removing some virus particles before they can fall out of the air and land on surfaces.

Lastly, it is also important to conduct evaluation. Building managers and business owners are encouraged to follow regulations and standards when it comes to performing Legionella hazard assessments. The CDC’s Legionella Environmental Assessment Form guides employers through conducting assessments in building water systems, determining whether Legionella environmental sampling is required, and, if so, develop a sampling plan. When conducting assessments, OSHA also suggests that when conducting assessments, employers should focus on:

  • Locations in the water systems where water is stagnant such as storage tanks, and components that have been isolated and no longer maintain a significant flow of water or infrequently used faucets.
  • Hot water recirculation systems.
  • Side-stream plumbing equipment not experiencing regular flow, such as expansion tanks, hammer arrestors, or by-pass lines.
  • Cross-connections between domestic and process water systems.
  • Backflow prevention devices.


  1. www.ccohs
  2. www.nhs.uk
  3. www.mayoclinic.org
  4. OSH
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