Bad durgo smell - PLS HELP

[Jlied03]

Have a loft conversion in old house and the bathroom vent pipe (with durgo?) Which is 1000mm above sink overflow was fitted in a sealed cupboard space next door. It's against the wall it smells so bad and there is black mold forming on the wall. See attached photo.
Is it the wrong attachment on top or do we need to elbow joint it out through the boarded wall into the old uninsulated loft space where there is ventilation ? PLEASE HELP AM DESPERATE

 

[Nige F]

It does look like the durgo is letting air out - as it should not. Easiest DIY fix is to buy a new one - cut the old one out and push the new one into the pipe . BUT that looks like a waste pipe size. We need a picture of the bottom of that pipe/connection to other pipes/soil pipe particularly. A Durgo should be on a 110mm vent pipe off of the 110mm soil pipe and ideally the 110mm vent should go through the roof to outside. As many pics as you like, the plumbers here will be able to advise.

 

[oilboffin]

Always better to vent to outside.