  The past twenty years have revealed the diversity of planets that exist in
the Universe. It turned out that most of exoplanets are different from the
planets of our Solar System and thus, everything about them needs to be
explored. Thanks to current observational technologies, we are able to
determine some information about the atmospheric composition, the thermal
structure and the dynamics of these exoplanets, but many questions remain still
unanswered. To improve our knowledge about exoplanetary systems, more accurate
observations are needed and that is why the Exoplanet Characterisation
Observatory (EChO) is an essential space mission. Thanks to its large spectral
coverage and high spectral resolution, EChO will provide exoplanetary spectra
with an unprecedented accuracy, allowing to improve our understanding of
exoplanets. In this work, we review what has been done to date concerning the
chemical modeling of exoplanet atmospheres and what are the main
characteristics of warm exoplanet atmospheres, which are one of the main
targets of EChO. Finally we will present the ongoing developments that are
necessary for the chemical modeling of exoplanet atmospheres.
