Hot Smoking and Cold smoking have been food preserving techniques for centuries. Cold Smoking and Hot Smoking are different processes. For cold smoke you want to be running a temperature around 20°C (68°F) or lower, so in summer this means cooling the cooking chamber.
US style “Smoked Meat” BBQ like Pork shoulder, Ribs, Brisket etc. are Hot smoked at a low temperature around 107C for long periods of time. The smoke required for this process is a feint wisp (The Thin Blue Smoke people talk about) of smoke over a 7 to 24 hour cook. Too much smoke or the wrong smoke will turn the food bitter as the Creosote in “White Smoke” or soot in “Black Smoke” deposits on the food. The method has a clean smoke travelling over the food continuously, ventilation is the key to true US style BBQ, allowing the air to enter the BBQ “Pit” and flow freely through, feeding the fire and picking up feint smoke on the way through.
Smallgoods can be Hot Smoked or Cold Smoked depending on what the product is you are trying to make, some are naturally cured, others use a nitrate cure. Pay attention to the specifics of the recipe, with smallgoods it is vitally important to follow the recipe exactly.
Electric and Gas smokers tend to smoulder the Smoke Source fuel (like woodchips or pellets) at the start, they fill the chamber with high density smoke, and heat the food within this smoke heavy environment. To ignite the woodchips/pellets you need a heat source directly under the Smoke Fuel, and this means that you are Hot Smoking generally. This process works well and produces a more “Smoked” tasting result than a BBQ’d result. Think Smoked Chicken Vs Pulled Pork, it’s a subtle difference.
Using a wood or charcoal fire gives a feint smoke environment and needs airflow, using Gas or Electric gives a heavy smoke environment with minimal airflow. Both are valid and both provide good results. Wood and Charcoal obviously takes a little skill to control, but if you are like me provides more fun, than flicking a switch. Not to say that I don’t still use Gas and Electric, I do, it depends on what I’m doing and the decision is heavily influenced by what time I have to monitor the cooking and/or fiddle with the fire and if I can be there to watch the process, this is perhaps where Electric has an advantage as you can leave it to do it’s thing. You would never leave a Gas or wood/charcoal cooker burning if you were not there.
Cold smoking is another process altogether. For cold smoke you need a low temperature, so no fire or heat to ignite woodchips inside the cooking chamber. The smoke can be generated by a Low heat generator like a pellet tube placed inside the cooking chamber, remembering that these internal devices need airflow to keep alight. You also need some method of keeping the chamber cool, how cool depends on the food you are smoking, cheese is in little danger of bacterial infection as is cured sausage, raw chicken and meats cannot stay in at room temperature for long periods. So we tend to pump cool smoke into a refrigerating chamber or we modify the environment to make it cooler, one easy way is to place a tray of ice with a couple of handfuls of pool salt sprinkled over inside the cooking chamber, this will rapidly cool the chamber, but it will create condensation.
In all these processes moisture is important as it helps to make the smoke adhere to the food and in some smokers also acts as a heat sink to help maintain a consistent temperature. The other thing to remember for Hot Smoking is that once the meat hits 65°C it stops taking on smoke itself, any glaze you apply will of course still accept smoke.
Smoke Ring, while it’s an attractive look, the development of a smoke ring is not part of smoking. The smoke ring is a result of Nitrates in the smoke “Curing” the outer layer of the meat and turning it pink (the same as cured ham is pink but roast pork is grey). You can “Cheat” this look by adding a little nitrate curing salt to the surface of the meat (in the rub, in the brine etc).