Diseases acquired from microbiologically contaminated airconditioning systems

An account of the design and function of airconditioning systems is provided in order to lay the foundation of study for the non-engineer. Certain components, particularly those containing large bodies of warm water, are prone to contamination with microorganisms. Such components are described because they present a hazard to the health of the building's occupants. Methods for collecting and handling specimens from these sources are included. Droplet nuclei less than 4.5um in diameter are the most likely particles to cause disease. They are distributed via the airhandling plant of the airconditioning system to all areas of the building. Particles of this size are able to evade the clearance mechanisms of the lung and be deposi ted in the finest airways where they can cause disease. There are two major diseases acquired from microbiologically contaminated air conditioning systems. Legionnaires' disease manifests as pneumonia and is caused by a gram-negative bacillus, the type species of which is Legionella pneumophila. Hypersensitivity pneumonitis is an allergic disease resulting from the inhalation of organic material. Lung dysfunction and a variety of generalized symptoms occur. Recommendations are made concerning the prevention of diseases from contaminated airconditioning systems and an approach is suggested towards their investigation.