This condition is usually caused by either kinked vent tubing, a restriction in the vent or too long of venting material from the area of where the dryer is located to the vent outside of the house. If the venting material is too long, the venting material should be shortened as much as possible. If the venting material appears to be short enough, you may have a restriction in the vent or the distance from the dryer vent to the outside is too long of a run. A quick way to test the vent airflow is to turn on the dryer without any clothes in the dryer. The amount of airflow should be equal to the amount of air exhausting from the dryer without the vent attached.nIf the problem persists, call us immediately to set up a service call.