G.A.S EC5 Fan Speed ControllerG. A. S EC5 Fan Speed Controller A brilliant thermostatic controller with RTT (Reactive Temperature Technology), the EC5 from G. A. S will intelligently increase or decrease fan speeds when there are changes to your preferred grow room conditions. Simply select a target temperature as well as minimum and maximum speeds for extraction and intake fans, then let it take care of the rest, whilst maintaining negative pressure courtesy of the built in fan