Inhalation therapy equipment may potentially act as a vector of hospital-acquired pneumonia due to gram-negative bacilli. The major mechanism by which bacteria are disseminated is aerosolization of organisms in particle sizes that are sufficiently small to be deposited in terminal lung units. Ventilators and humidifiers are relatively innocuous in this regard, and small-volume Venturi nebulizers (medications nebulizers) are not frequently incriminated in nosocomial epidemics. Large-volume nebulizers of all designs (Venturi, spinning disk, or ultrasonic) are the primary source of aerosolized bacteria. The method of decontamination differs with nebulizer design, but any system of decontamination must be carried out at least once every 24 hours while the equipment is in use. No hospital can consider its procedure of decontamination satisfactory unless it has a continuing monitoring program to demonstrate that the degree of contamination does not exceed that of hospital air.
Alan K. Pierce, Jay P. Sanford. Bacterial Contamination of Aerosols. Arch Intern Med. 1973;131(1):156–159. doi:10.1001/archinte.1973.00320070152017