  Thermochemical equilibrium is one of the most commonly used assumptions in
current exoplanet retrievals. As the James Webb Space Telescope (JWST) and
Ariel launch draw near, assessing the underlying biases and assumptions made
when applying self-consistent chemistry into spectral retrievals is crucial.
Here we use the flexibility of TauREx 3.1 to cross-compare three state of the
art chemical equilibrium codes: ACE, FastChem and GGchem. We simulate JWST
spectra for ACE, FastChem, GGchem and GGchem+condensation containing only C, H,
O, N elements and spectra for FastChem, GGchem and GGchem+condensation with a
more extensive range of elements giving seven simulated JWST spectra in total
and then cross-retrieve giving a total of 49 retrievals. Our analysis
demonstrates that like-for-like, all chemical codes retrieve the correct
parameters to <1% of the truth. However, retrievals, where the contained
elements do not match the truth, parameters such as metallicity deviate by 20%
while maintaining extremely low uncertainties <1% giving false confidence. This
point is of major importance for future analyses on JWST and Ariel,
highlighting that self-consistent chemical scheme that do not employ the proper
assumptions (missing species, fixed elemental ratios, condensation) are at risk
of confidently biasing interpretations. Free chemistry retrievals employing
parametric descriptions of the chemical profiles can provide alternative
unbiased explorations.
