It's an outlet shaped like a fir tree. Det er et afløb dannede ligesom et grantræ.

I looked at the references below and it seems to be called afgangstilslutningen. I suppose you'd still call it fir tree because other similar valve/connection arrangements such as the "christmas tree" still keep the English when translated to Danish.

http://www.airliquide.dk/en/business/pdf1/Dim.pdf
http://www.flemingmedical.ie/regulators.htm
http://www.bocmedical.co.uk/safety/basic_safety/general_info...