[M.Acorn]

Not me mind  Think the carpet had been cleaned before,and custy must have replaced furniture without isolating it.
Tried a few products on it,but nothing made any difference at all...

[John Kelly]

That may be BHT yellowing Mark. Its caused by the chemicals off gassing from the underlay and carpet backing discolouring the fibres as they are trapped in the pile by the furniture. Acetic Acid sometimes moves it but its often permanent.

[M.Acorn]

That makes sense,and is probably what it was,reasonably new house

[Carpet Dawg]

That may be BHT yellowing Mark. Its caused by the chemicals off gassing from the underlay and carpet backing discolouring the fibres as they are trapped in the pile by the furniture. Acetic Acid sometimes moves it but its often permanent.

Thats pretty scary...

Will using foam blocks (i.e. leaving a gap between the carpet and furniture for air to flow) stop this John?

Tony

[M.Acorn]

Glad to have brick floors where I live then,pretty scary that people breath that in

[Simon@arenaclean]

interesting link here and seems to agree there is a limited period after fitting it could be a problem http://www.allergyconsumerreview.com/carpet-air-quality.html Allowing good ventilation for a couple of days should be fine and raising heavy furniture will certainly help. I've never experienced this in carpets i've cleaned it should of cleared long before we get to it. Goes without saying good ventilation after cleaning is essential, i've doubled up snap blocks on furniture that is less than an inch of the ground just to make sure and aid circulation.

[Mike_Roper]

More common under rugs or entrance mat in the form of yellowing, also read that acid can reverse it.
Mike

[M.Acorn]

I think the reason it was so bad,was because there was no ventilation under whatever was on top,looks like it had contact all the way around,nothing shifted it,didn`t get any transfer,but I possibly shouldn't have been looking for transfer,with it being caused by off gassing

[Hilton]

It could quite easily have been a leak from the rad that it sits next to, have you pulled the carpet back and had a look?.