Absolute electron loss cross sections have been measured for fast hydrogen atoms incident on He, H2, N2, O2, CO, CO2, and CH4 in the 0.25- to 5-keV energy range important in studies of proton aurorae. The fast hydrogen of fast protons arising from electron loss collisions of these H atoms with the target gas was measured. Particular attention was paid to complete collection of product ions and to elimination of effects resulting from nonuniform pressure distributions near the gas cell orifices. Techniques for absolute determination of fast hydrogen atom flux are also described.