An H

In a series of two papers we present results of a new Hα imaging survey, aiming at the detection of extraplanar diffuse ionized gas in halos of late-type spiral galaxies. We have investigated a sample of 74 nearby edge-on spirals, covering the northern and southern hemisphere. In 30 galaxies we detected extraplanar diffuse emission at mean distances of $|z|\sim1{-}2$ kpc. Individual filaments can be traced out to $|z|\leq6$ kpc in a few cases. We find a good correlation between the FIR flux ratio ($S_{60}/S_{100}$) and the SFR per unit area ($L_{\rm FIR}/D^2_{25}$), based on the detections/non-detections. This is actually valid for starburst, normal and for quiescent galaxies. A minimal SFR per unit area for the lowest $S_{60}/S_{100}$ values, at which extended emission has been detected, was derived, which amounts to $\dot{E}_{\rm A25}^{\rm{thres}} = (3.2\pm0.5)\times10^{40}\rm{\,erg\,s^{-1}\,kpc^{-2}}$. There are galaxies where extraplanar emission was detected at smaller values of $L_{\rm FIR}/D^2_{25}$, however, only in combination with a significantly enhanced dust temperature. The results corroborate the general view that the gaseous halos are a direct consequence of SF activity in the underlying galactic disk