  A photoionized gas under constant pressure can display a thermal instability,
with three or more solutions for possible thermal equilibrium. A unique
solution of the structure of the irradiated medium is obtained only if electron
conduction is considered. The subject of our study is to estimate how the
effect of thermal conduction affects the structure and transmitted spectrum of
the warm absorber computed by solving radiative transfer with the code TITAN.
We developed a new computational mode for the code TITAN to obtain several
solutions for a given external conditions and we test a posteriori which
solution is the closest one to the required integral condition based on
conduction. We demonstrate that the automatic mode of the code TITAN provides
the solution to the radiative transfer which is generally consistent with the
estimated exact solution within a few per cent accuracy, with larger errors for
some line intensities (up to 20 per cent) for iron lines at intermediate
ionization state.
