  The quantum evaporation of primordial black holes may have a relevant effect
on the reionization of the Universe at small redshifts ($z \leq 60$): in this
paper, I studied the possibility of a reionization induced by the photons
emitted during the last stages of the black holes life. I also took into
account the quark and gluons jets production, that sensibly modifies the
blackbody Hawking emission spectrum. In this way, one obtains a ``late and
sudden'' reionization process, characterised by a very well controlled rise of
the plasma temperature: the plasma heating is not so high to induce a strong
distortion of the CBR spectrum, in agreement with the recent FIRAS upper limit
on the comptonization parameter.
