monotonic velocity law. These are the radio free-free emission (typically arising far out in the wind), H$\alpha$ emission (primarily located near the star) and the UV wind lines (which sample the entire wind). In an ideal scenario all three diagnostics would agree. However, strong clumping in the winds can cause them to deviate from one another. Clumping can cause H$\alpha$ and radio observations to [*overestimate*]{} mass loss rates, since both of these diagnostics contain density-squared terms. At the same time, clumping can cause the UV line absorption to [*underestimate*]{} mass loss (e.g. Oskinova et al. 2007).

In the present study we re-examine the effects of clumping in the measurements of mass-loss rates derived from UV resonance line profiles. Clumping leads to porosity in both velocity and space [^1] (e.g. Oskinova et al. 2007; Sundqvist et al. 2010, Šurlan et al., 2012) i.e. irregularities in the opacity of the wind material that covers the stellar disk at a certain velocity and accounts for the absorption that we measure. These irregularities will allow channels of reduced opacity (or increased transmission) to be present and thus distort our interpretation of the line-synthesis modelling of the UV absorption troughs. An observed wind-formed UV resonance 