I've read on this forum that the outside plastic of the UCG's is made of PVC. That is harmfull because after a certain amount of time, PVC can liberate some gases which discolours the cover.
Does someone who have UCG's for some considerable time, like 1 or 2 years, can prove this fact? If able, post some pictures. I want to know if that is really true, because I read somewhere else that not all kinds of PVC can cause this damage.