No fan. It's connected to the electric burners. AMNPS for smoke, two electric burners connected to the PID controller for temp, I can leave it overnight without more than 2-3 degrees of temperature excursion.
I am sure you could use it on a wood burner with a fan, kicking the fan on to cool, but I chose electric. I don't need 20 pounds of wood for 12 hours of smoke, I need a pound of pellets in the AMNPS.
Biggest problem is that with an uninsulated barrel, I need about 2kW to get 240F, which means I either need to supplement with a small fire, or put an insulation blanket over it, or power the second burner from another circuit. Because 20A at 110 is about 2kW But I can get about 220F out of the single burner, and if I need higher temp, I add a small burner from a metal hot plate and run the power to another circuit. I rarely need hotter than 220, so I just run the one burner.
If I was only hot smoking and didn't want tight temp control (I do because I smoke a lot of sausage) I would forgo the PID controller completely, because 1500W in a UDS gets you pretty a pretty good smoking temp of 220F.
Cool part is I can use the same dang controller connected to my 5 gallon bucket and hot water heater element Sous Vide cooker.