A dryer vent should be checked often to make sure that no lint has built up inside it. Lint build-up is a serious fire hazard. So, why does lint come out of your dryer vent?
If you want to see why lint is coming out of your dryer, then place a brand new, brightly colored garment in your dryer. After it dries for a while take it out and you will see lint that is the same color as your garment that is now been collected in the lint trap.
Lint is the buildup of fibers from the clothes that get tossed and turned in your dryer. It doesn't matter what you put in your dryer, the fibers will come loose after heat is applied and the garment is constantly tossed and turned by the dryer drum.
Cleaning the Vent Line
Dryer lines need to be cleaned periodically. Lint will build up to some degree no matter what. There are devices available in your local hardware store that will help you clean out the vent line or you may want to hire a professional to do the job.