Solvent Desorption from Carbon Beds in Ducted and Nonducted Laboratory Fume Hoods

Abstract

Abstract To assess the magnitude and speed of desorption of adsorbed vapors from commercial carbon beds used in laboratory hoods, known quantities of organic solvents were evaporated in one ducted (i.e., exhausted to the outside) and two nonducted (i.e., recirculating) laboratory fume hoods. The air downstream of the filters was then sampled and analyzed. Benzene (BZ), carbon tetrachloride (CT), and ethyl acetate (EA) were individually volatilized at room temperature in a ducted chemical fume hood at 6, 4, and 5 ppm, respectively. BZ and EA were released twice; CT was released four times. The total amount of vapor desorbed, as a percentage of the mass released, ranged from 10 percent for the first BZ release to 100 percent for the fourth CT release. BZ, CT, and n-hexane (HX) were simultaneously volatilized in nonducted laboratory fume hoods at 10, 50, and 125 ppm, respectively, over six 4-hour periods, with each 4-hour release followed by 4 hours of vapor-free air (88 hours of vapor-free air after the six...