This compound deletes particles when they reach the age limit (AgeLimit attribute) that is set in the Set Particle Age Limit compound. You need to first have the Set Particle Age Limit compound plugged into the Emit compound's Execute on Emit port so that the ICE tree knows what the particle's age limit is.
Plug this compound's Execute output into the ICETree node.
For more information on deleting particles, see ICE Particle Age [ICE Particle Simulations].