We simulate the ionization environment of z \sim 20 luminous objects formed within the framework of the current CDM cosmology and compute their UV escape fraction .
These objects are likely single very massive stars that are copious UV emitters .
We present analytical estimates as well as one–dimensional radiation hydrodynamical calculations of the evolution of these first HII regions in the universe .
The initially D–type ionization front evolves to become R–type within \lesssim 10 ^ { 5 } yrs at a distance \sim 1 pc .
This ionization front then completely overruns the halo , accelerating an expanding shell of gas outward to velocities in excess of 30 km s ^ { -1 } , about ten times the escape velocity of the confining dark matter halo .
We find that the evolution of the HII region depends only weakly on the assumed stellar ionizing luminosities .
Consequently , most of the gas surrounding the first stars will leave the dark halo whether or not the stars produce supernovae .
If they form the first massive seed black holes these are unlikely to accrete within a Hubble time after they formed until they are incorporated into larger dark matter halos that contain more gas .
Because these I–fronts exit the halo on timescales much shorter than the stars ’ main sequence lifetimes their host halos have UV escape fractions of \gtrsim 0.95 , fixing an important parameter for theoretical studies of cosmological hydrogen reionization .