How to find it
From parking for Aven Reynaud, follow road until GR4 track is seen heading off to the left (red/white stripe). Turn in; parking shortly afterwards on left. Follow track to first junction; take left fork. Some distance on (*) there is an obvious track on the left, marked high up with a sign with "Vigne Close" in feint writing. Take the track; a small fork goes off on the right, but follow the main track to suddenly arrive at the hole in a copse.
See Speleo Sportive en Ardèche. Apparently there are three parallel shafts at first and one needs to follow the right one!
High levels of carbon dioxide occur near the bottom.