An air removal unit configured for removing exhaust air from an equipment rack or enclosure includes multiple fans to achieve a high airflow capacity while defining a compact and portable structure. The inverters of the circuit are made up of an NMOS transistor and a PMOS transistor. When the quick release is in a released position, relative sliding movement between the quick release and the arcuate tube is allowed. The energized etching gas is introduced into the process zone to etch the double patterning features to form a solid residue on the substrate. Preferably, rotating and oscillating light signals are produced by sequentially illuminating columns of LED’s on a stationary light support.