QEL is the motorized latch retraction option for Von Duprin exit devices.  QEL is used when automatic latch retraction is needed, such as when used with access control so that the door can be pulled open following a valid credential. 

Chexit is a delayed egress option for Von Duprin exit devices.  This option delays a door from opening for a prescribed period of time when the exit device is pressed.  Chexit must be installed and configured in accordance with all applicable codes.   Click HERE for an overview video. 

QEL and Chexit can not both be added to a single exit device; only one of these functions can be selected.