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Halpha and UBV photometry of the inner kpc of M33 are used to study thedistribution of OB stars and HII regions in the galaxy and to determine whetherindividual regions of the galaxy are in a state of ionization balance. Based onthe surface brightness of the Halpha emission, we identify three distinctionized gas environments (bright, halo and field). We find that 50% of the OBstars are located in the field, so that 1/2 of the lifetime of OB stars must bespent outside recognizable HII regions. If OB stars escape from bright HIIregions by destroying their parent molecular clouds, this result would implythat molecular cloud lifetimes after forming OB stars could be as low as 5e6yrs or 1/2 the typical lifetime of OB stars. Halpha fluxes predicted fromionization models reveal that none of the regions are in ionization balance:predicted fluxes are a factor of 3-7 greater than observed. The heaviest lossof ionizing photons appears to be taking place in the field. Our resultssuggest that star formation rates obtained from Halpha luminosities mustunderestimate the true star formation rate in these regions of M33.Comment: Replaced version should now compile with standard aastex style files.  23 pages, aastex preprint format. Accepted in ApJ. Hardcopies of figures  available on request to wilson@physics.mcmaster.c

Are Galaxies Optically Thin to Their Own Lyman-Continuum Radiation? I. M33