You need to use either:
Prochem 'Filter out' or Prochem Ultrapac-renovate. Sometines Solution UK's 'Eco-spotter' works too.
I had a customer only last week with really bad draught marking all around the perimiter of a 23x12 lounge/diner, plus two lines that ran right down the middle of the room.
She said to me, ''oh, they won't come out, coz the last two times we've had the carpets cleaned, both CC's have said there's nothing they can do!!!
I didn't promise anything (even though I was pretty confident they'd come out)
Guess who's the hero now
