Two commercially available nebulizing devices used for ventilation studies were evaluated. The nebulizers use radioactive Technetium-99m (Tc99m), a potential source of room air contamination. Ambient air concentrations of Tc99m were monitored, as were the exposures of department personnel not performing ventilation studies. Room surfaces and air vents were examined to determine the extent of contamination in the examination room. Personnel were evaluated for contamination on clothing, hair, and airways when hospital lab coats and latex gloves were the only protective apparel used. Though the maximum permissible concentration of 4 x 10(-5) microCi/c3 was not exceeded, preliminary results indicated levels as high as 11,000 disintegrations/min in the nasal passages of personnel. These findings clearly demonstrate the need for more effective personal protective devices. Personnel contamination resulted primarily from the patient, due to an inability to maintain a proper oral seal on the nebulizer mouthpiece. Conventional hospital surgical masks were ineffective in reducing internal deposition to tolerable levels. By comparison, levels were reduced by 19% (p > 0.10) through use of methods such as simple body substance isolation techniques and high-efficiency disposable respirators. Levels approaching 50 disintegrations/min or less were obtainable (p < 0.001), and overall levels of Tc99m were reduced by 78%.