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tokens: of any model for distributions of the properties of the clouds in the BLR. In fact, in the current analysis, our only constraint is to suppose that all the hydrogen lines are emitted from the same clouds with certain density and excitation conditions, which is a reasonable assumption considering the similarity of the profile of the various H i lines we analysed for each object. Additionally, if more than one grid point is a good match to the data, we adopt a simple weighting scheme where we calculate median Φ H , n H and line ratios from these point. A detailed description of our photoionization modelling scheme is given in Section 3.3 . 3.3 Extinction measurements The extinction affecting a set of line ratios may be determined by comparing the measured ratios with their theoretically predicted intrinsic values. In the case of the He ii lines, considering the He ii λ4686/He ii λ10 126.4 line ratio is expected to be similar to the case B prediction even in the BLR spectrum (Bottorff et al. 2002 ), we estimate the extinction to both the NLR and BLR assuming an intrinsic He ii λ4686/He ii λ10 126.4 line ratio of 3.77, corresponding to the case B prediction for a temperature of 10 000 K and a density of 10 6 cm −3 . If broad He ii λ4686 Å is not observed, we estimate a lower limit to A V (BLR) based on the broad He ii λ10 126.4 Å flux. This was done decreasing the observed broad He ii λ4686/He ii λ10 126.4 ratio in steps of 0.1, starting from the intrinsic value of 3.77, until the broad He ii λ4686 Å line becomes indistinguishable from the continuum. The lower limit to the extinction is then derived from this ratio. In Table 2 , we list A V (NLR) and A V (BLR) as estimated from the He ii lines for each object. The errors in these estimates were derived assuming an uncertainty of 20 per cent in the observed line ratios. Table 2. Extinction to the narrow-line region, A V (NLR), and extinction to the broad-line region, A V (BLR), derived from Balmer and Paschen H i line ratios and the He ii λ4686/He ii λ10 126.4 line ratio as described in Section 3.3 . In objects where broad He ii λ4686 is not detected, a lower limit to A V (BLR) was determined from broad He ii λ10 126.4 Å. These lower limits are marked with an asterisk. Abbreviated name: MCG–05-14-012, MCG–05-23-16 and MCG–06-30-015. In the case of the H i lines, determining A V (NLR), is a straightforward process since, as outlined in Section 3.1.3 , a fixed set of intrinsic line ratios can be assumed. Deriving the extinction A V ( NLR ) to the NLR was done during the step of fitting and subtracting the narrow lines as described in that section. In Table 2 , we list A V (NLR) as estimated from the H i lines for each object. The errors in A V estimates were derived assuming an uncertainty of 20 per cent in the observed line ratios. The extinction to the BLR is derived in a different way, since the H i intrinsic line ratios are not known. To do so, we followed these steps. We compared the