@SeaCow52 I haven't done Ash and Trash, but for persistent smoke on an object, I place this in the Init of the object (wreck, hut, rubble, etc.):
TheObject = "test_EmptyObjectForSmoke" createVehicle position this;
TheObject attachTo[this,[0,1.5,-1]];
For persistent fire:
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TheObject = "test_EmptyObjectForFireBig" createVehicle position this;
TheObject attachTo[this,[0,1.5,-1]];
Now I am thinking you are talking about persistent colored smoke: have you tried the Smoke Grenade module under Systems (F5) / Effects...enable permanent effect?