Years ago (about 1990 I think) I built a great cold smoker out of an old electric oven - the old stand-alone type).
From memory I just removed the elements and inserted a tube approx 2" in diameter in the back at the top.
The oven already had racks for the fish. You salted the fish quite heavily and sprinkled on a bit of brown sugar, then spread medium sawdust about 15mm thick on the bottom of the oven, lit it in one corner so it started to smolder, and threw the fish in on the racks.
It would smolder away for about 6 hours and when you took the fish out it was absolutely melt in your mouth delicious :)
The trick was to get the vent hole just the right size so that the sawdust got enough oxygen to keep smoldering, but not enough so that it started to burn.
Thinking about it I may have ended up with one tube at the top of the oven and one at the bottom to induce some airflow.
Years before that at school we made the hot smokers that look like a metal box with a lid that you put sawdust into and put a dish of metho underneath.
Only takes about 20-30 mins.
Completely different taste/textures. The cold smoker fish was very smoky and soft, whereas the hot smoked fish was more steamed with slight smoke flavour.
SteveG

