I do the carpets in 3 -20 story buildings. A great company, pays well and on time and they didn't complain about this , but it bugs me. In every one of them, the halls ( nylon cut pile commercial) have edges with what looks like filter soiling, but it comes out 3 inches. It will not move. I've tried every thing I can think of. Citrus solve, high alkaline, shampoos, encaps, acids, ultrapac renonovate, screaming hot rinses, hand scrubbing,high pressure, low pressure, and the list could go on. It just will not move.
Here's a pic of what it looks like, my camera didn't catch it well enough. Sloppy painter got the hinge.
Here's a pic of what it looks like, my camera didn't catch it well enough. Sloppy painter got the hinge.