How can you remove "sooty" stain from carpet around floor molding?

I would use some foam carpet cleaner, I love the Dollar Tree one, and use a soft carpet brush. That carpet cleaner cleans up anything I use for my clients houses. Its the HomeStore brand, its so good, I brought a case. I just cleaned a clients' carpet huge grease spots that the professional carpet cleaner did not get up.... two applications and it was gone.

Try these ideas:

http://www.howtocleanstuff.net/how-to-remove-soot-from-carpet/

http://www.sfgate.com/homeandgarden/article/Washing-that-soot-right-out-of-carpet-hairs-2774565.php

http://www.howtocleanstuff.net/how-to-remove-soot-from-carpet/

I might not be soot... it might be mold especially if on an exterior wall...

.....My son had that dark line around his carpet when he moved into his home and we investigated it and found that supposedly it is caused by your (his) heating system. I have found my hallway gets this darkish stain and I just clean it with rug cleaner....it will come back in time (year or so) but is easy to clean. Don't know what the preventive would be...we just put in a new heating system so will see if that prevents the darkish stain.

Woolite carpet cleaner might work. Spray it on and rub with an old toothbrush. Let it dry and then vacuum. You may need to repeat several times. Best of luck!

Try using a stiff thick paintbrush, it could be just dust. Then use a damp rag and go back and forth over the area. I have wall to wall in some rooms as well and there always seeto do be a dark line right near the baseboard. Mine is usually dust.

that probably dust from the hvac. had a lot of it showing up. try caulking the base boards

My daughter has the same problem. the carpet cleaner company said its from the flooring and not being airtight. Drafts and small spots where they missed getting things tight. It came out when they had the carpets cleaned but was back within a few months..

Use 1/4 cup of white vinegar, 1 tbsp. of Dawn dish soap, and fill with water. Spray area liberally and let soak for 5-10 minutes and then proceed with blotting with a clean, dry towel until stain is removed. Some carpet stain removal products can be of great benefit for combating many types of carpet stains.