The authors describe a vacuum apparatus for determining the outgassing rate into vacuum, the diffusion coefficient, and the amount of gas absorbed for various materials. The diffusion coefficient is determined from a model applied to time-dependent desorption data taken using a throughput method. The authors used this method to determine the diffusion coefficient, D, for H2O in three dimensional printed acrylonitrile butadiene styrene (ABS). They found D-H2O = 8.3 x 10(-8) cm(2)/s +/- 1.3 x 10(-8) cm(2)/s (k = 1; 67% confidence interval) at 23.2 degrees C. This result was compared to the diffusion coefficient determined another by a gravimetric method, in which the sample weight was monitored as it absorbed gas from the atmosphere. The two methods agreed to within 3%, which is well within the uncertainty of the measurement. The authors also found that at least 80% of the atmospheric gas (air) absorbed by the ABS is water. The total amount of all atmospheric gas absorbed by ABS was about 0.35% by weight when exposed to ambient air in the laboratory, which was at a pressure of 101 kPa with a relative humidity of 57% at 22.2 degrees C. (C) 2016 American Vacuum Society.