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Using the short-high module of the Infrared Spectrograph on the Spitzer SpaceTelescope, we have measured the [S IV] 10.51, [Ne II] 12.81, [Ne III] 15.56,and [S III] 18.71-micron emission lines in nine H II regions in the dwarfirregular galaxy NGC 6822. These lines arise from the dominant ionizationstates of the elements neon (Ne$^{++}$, Ne$^+$) and sulphur (S$^{3+}$,S$^{++}$), thereby allowing an analysis of the neon to sulphur abundance ratioas well as the ionic abundance ratios Ne$^+$/Ne$^{++}$ and S$^{3+}$/S$^{++}$.By extending our studies of H II regions in M83 and M33 to the lowermetallicity NGC 6822, we increase the reliability of the estimated Ne/S ratio.We find that the Ne/S ratio appears to be fairly universal, with not muchvariation about the ratio found for NGC 6822: the median (average) Ne/S ratioequals 11.6 (12.2$\pm$0.8). This value is in contrast to Asplund et al.'scurrently best estimated value for the Sun: Ne/S = 6.5. In addition, wecontinue to test the predicted ionizing spectral energy distributions (SEDs)from various stellar atmosphere models by comparing model nebulae computed withthese SEDs as inputs to our observational data, changing just the stellaratmosphere model abundances. Here we employ a new grid of SEDs computed withdifferent metallicities: Solar, 0.4 Solar, and 0.1 Solar. As expected, thesechanges to the SED show similar trends to those seen upon changing just thenebular gas metallicities in our plasma simulations: lower metallicity resultsin higher ionization. This trend agrees with the observations.

Spitzer observations of extragalactic H II regions - III. NGC 6822 and the hot star, H II region connection