A number of very small isolated H ii regions have been discovered at projected distances up to 30 kpc from their nearest galaxy .
These H ii regions appear as tiny emission line objects in narrow band images obtained by the NOAO Survey for Ionization in Neutral Gas Galaxies ( SINGG ) .
We present spectroscopic confirmation of four isolated H ii regions in two systems , both systems have tidal H i features .
The results are consistent with stars forming in interactive debris due to cloud-cloud collisions .
The H \alpha luminosities of the isolated H ii regions are equivalent to the ionizing flux of only a few O stars each .
They are most likely ionized by stars formed in situ , and represent atypical star formation in the low density environment of the outer parts of galaxies .
A small but finite intergalactic star formation rate will enrich and ionize the surrounding medium .
In one system , NGC 1533 , we calculate a star formation rate of 1.5 \times 10 ^ { -3 } M _ { \odot } yr ^ { -1 } , resulting in a metal enrichment of \sim 1 \times 10 ^ { -3 } solar for the continuous formation of stars .
Such systems may have been more common in the past and a similar enrichment level is measured for the ‘ metallicity floor ’ in damped Lyman- \alpha absorption systems .