A TEST CHAMBER FOR EXPERIMENTAL HYDROGEN-FLUORIDE EXPOSURE IN HUMANS

An inhalation chamber was built to perform experimental studies with h ydrogen fluoride (HF), other gases,and particulate matter. The present study sought to describe a new gas delivery system and the distributi on and concentration of HF gas in the chamber. The aluminum chamber ha s a volume of 19.2 m(3) and a variable ventilation rate of about 1 to 10 air changes per hour. The negative pressure difference between the chamber and outside air can be regulated from 0 to 300 Pa. HF was fed at concentrations of up to 4000 mg/m(3) directly into the ventilation duct feeding the chamber through openings with diameters as small as 5 0 mu m, oriented opposite to the airflow. Gas flow was varied from abo ut 0.1 dm(3)/min at a pressure of 4 arm. The dilution factor of HF con centration from cylinder to chamber was on the order of 10(3) to 10(4) . The standard deviation (SD) of the HF concentrations at a fixed meas urement point during a hour test was typically 0.05 mg/m(3) at a time- weighted average (TWA) concentration of 2.66 mg/m(3). The SD of the TW A HF concentrations at six locations in the chamber was typically 0.05 mg/m(3) and 0.29 mg/m(3) at 0.61 and 3.46 mg/m(3), respectively. Huma n exposure could be predicted from calculations based on ventilation d ata, gas flow, and observed ratio between calculated and measured conc entrations. When the target exposure concentration was 1.5 mg/m(3), th e measured mean exposure concentration was typically 1.54 mg/m(3) (ran ge: 1.4-1.7 mg/m(3), SD 0.09 mg/m(3), n=8). The chamber is well-suited for inhalation studies in humans. Chamber atmosphere was controlled a nd has proved to be stable and homogeneous, even in tests with HF, a h ighly reactive gas in the class of superacids.