Centrifugal blowers require a scroll to enclose the impeller to generate pressure. Air enters axially and exits radially while being directed at a focused right angle for spot cooling. Centrifugal blowers generally have a low airflow and high pressure. Efficiency is lower than that of axial fans and the impeller is typically smaller as well. Noise concerns must be taken into account when considering these fans as they have much higher noise levels. Centrifugal fans are used in networking, telecommunications, and high performance personal computers.