Rate coefficients for the reactions of He(23S) atoms with N2, O2, CO, and CO2 were determined by measuring the fractional absorption of 3889 Å light from a helium lamp as a function of the concentration of the neutral gas in a flowing afterglow apparatus. The rate coefficients are in reasonable agreement with those obtained previously from measurements of the emission intensity. It is concluded that the observed chemiluminescence arises from Penning ionization reactions involving the He(23S) atom.