combination of increased thermal dust emission along with a wavelength dependent absorption, which, in highly obscured sources, may decrease their K band flux. Such an example is Arp220 which displays a ratios f$_{15\mu m}$/K$\sim $30 [@Charmandaris2002]. Two more ratios of the LW3 and LW2 over the H$\alpha$ line flux density are also included in Table \[k\_ha\] for reasons of completeness. It has been established that in normal spirals, both filters mostly trace the MIR flux arising from the reprocessing of ionising radiation which is observed in the optical via the H$\alpha$ line [@Sauvage1996; @Roussel2001; @Dale2001]. Since in more active galaxies, the H$\alpha$ emission is strongly affected by the absorption, these ratios could be used to quantify the level of absorption[^3] even though one should be cautious in their quantitative interpretation since the ratios may saturate toward extreme starbursts [@Roussel2001]. We present the LW2/H$\alpha$ mainly for comparison, as the most interesting indicator is clearly the one involving the LW3 filter which directly traces the continuum of hot dust emission emitted by the small grains.

[lcccc]{}Target & & & &\
& H$\alpha$ & K & H$\alpha$ & K\

IRAS 19254-7245(S)& 91.3 & 12.4 & 224.5 & 30.4\
IRAS 19254-7245(N)& 78.4 & 1.2 