Metal deficiency in the H i region δ_H   i as a function of the fraction of hydrogen present in the HI-ex component defined as the extended H i component that may be less enriched in metals as compared to HI-sf (the H i component associated to the star-forming regions). We assume that the HI-sf component has the same metallicity as the H ii region and calculate δ_H   i for several values of the sulfur abundance ratio between HI-ex and HI-sf. The horizontal dashed line and the grey stripe indicates illustrate the sulfur deficiency, δ_H   i(S) = 0.18 ± 0.11.