RP: http://wiki.openstreetmap.org/wiki/Tag:man_made%3Dmineshaft?
i'm not sure about the tunnel vent. either we create man_made=tunnel_vent, or re-work man_made=mineshaft to be more generic i.e. man_made=shaft. the first is way easier, and not objectionable imo.
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HB: the LINZ example is a ventilation shaft. man_made=shaft ??
see also http://wiki.openstreetmap.org/wiki/Tag:man_made%3Dmineshaft