We cleaned this vent a year ago and came back, at the clients request, to see if there was any lint accumulation over the past year.  If you notice, the air velocity had gone from 17.x to 19.x.  This is because, when you clean the lint with the brush and vaccum method, as most local dryer vent cleaning companies do, the lint in the dryer lays undisturbed.  Once the back pressure in the vent is eliminated, and air flow is restored, the dryer will eventually release the lint inside of it, restoring the dryer’s full potential.

This is also one of the big reasons we have upgraded our equipment to a positive air method.  Now, when the hose reaches the back of your dryer, the 30 cubic feet  per minute of positive airflow with a reverse oscillation nozzle at 175 pounds per square inch agitates the lint inside the dryer so we can easily eject it from the machine.

nonetheless, after a year, this dryer vent was not ready to be cleaned.  We just removed the small build up from the damper inside the gooseneck and recommended a visit at a later date.