is it normal

There is usually some underlying condition that causes them. They keep returning until it's corrected

Or a furnace issue

You tell the customer the guy who put down the carpet didn't put a large enough quarter round , sell her an 1&1/2  inch quarter round and charge for installation...................you guys will never make money , it's not all about carpet cleaning...................it's about being creatiive

Edited by nightrider - 07/February/2008 at 12:45pm

SELL HER NEW CARPETS AFTER A COUPAL OF YEARS , PLUS AN AIR PURIFIER , EXPLAIN THAT'S WHAT MAKING ALL THAT BLACK CRAP ON HER CARPETS

unless you properly seal the air spaces it will continue.  After all it is air movement that is creating the filtration lines in the first place.  may moons ago people would shut doors in parts of the house they did not want to heat. In the spring if the carpet was a light colour they would have a filtratiion line under the door. there would also be lines under the closet doors.  That to me is a selling point of carpet. If the carpet was not filtering all those contaminates out of the air you would be breathing them in.  Your carpet must be cleaned to remove all thos contaminates to make your home healther. If you had hardwood or laminates you would already have all that black in you and your child's lungs. so what is more healther??  I myself don't waste time on filtration lines ??

Now you're talking

Now you know it too