  We study fluctuation fields of orthogonal polynomials in the context of
particle systems with duality. We thereby obtain a systematic orthogonal
decomposition of the fluctuation fields of local functions, where the order of
every term can be quantified. This implies a quantitative generalization of the
Boltzmann Gibbs principle. In the context of independent random walkers, we
complete this program, including also fluctuation fields in non-stationary
context (local equilibrium). For other interacting particle systems with
duality such as the symmetric exclusion process, similar results can be
obtained, under precise conditions on the $n$ particle dynamics
