PAH luminosities (L_PAH/L_∗) compared to the I_6.2/I_11.3 ratio for the benchmark modeling grid (left) and the observations of Herbig stars (right). Several parameters of the benchmark model are varied and their effect to the PAH luminosity and I_6.2/I_11.3 ratio is shown. The main results of the benchmark modeling grid study is that in general the PAH neutral fraction is high and ionized PAHs originate from optically thin, low density environments. The red dots show the objects studied in this paper. The parameters of all the objects shown in this right plot are listed in Table 1.