  We discuss the role of recombinations in the IGM, and the related concept of
the clumping factor, during cosmic reionization. The clumping factor is, in
general, a local quantity that depends on the local over-density and the scale
below which the baryon density field can be assumed smooth. That scale, called
the filtering scale, is itself depended on over-density and local thermal
history. We present a method for building a self-consistent analytical model of
inhomogeneous reionization assuming the linear growth rate of the density
fluctuation, which accounts for these effects simultaneously. We show that
taking into account the local clumping factor introduces significant
corrections to the total recombination rate, comparing to the model with a
globally uniform clumping factor.
