Contaminated respiratory therapy equipment may be responsible for the spread of pathogens to hospital patients. This study focused on the potential for contamination of prefilled, sterile, disposable water and saline systems for humidification and nebulization. Gas and liquid samples from 48 prepacked oxygen humidifier/cannula and 26 prepacked nebulization setups were taken at the initial application of devices and at 8, 24, 48, and 72 hour intervals, totaling 386 cultures. All samples from the humidifier units were found to be pathogen-free for up to 3 days. A total of six or 3.84% of the nebulizer samples showed contamination with Enterobacter cloacae after 8 to 24 hours of operation. It was concluded that the potential for contamination of the humidifiers is low for up to 72 hours, but the nebulizer units should be changed after 24 hours even though their contamination rate is markedly lower than that of conventional nondisposable units.