Historically, farms in the Western world included a small building termed the "smokehouse," where meats could be smoked and stored. This was generally well-separated from other buildings both because of the fire danger and because of the smoke emanations; the smoking of food could possibly introduce polycyclic aromatic hydrocarbons which may lead to an increased risk of some types of cancer; however, this association is still being debated. [disputed – discuss]
Smoking can be done in four ways: cold smoking, warm smoking, hot smoking, and through the employment of "liquid smoke." However, these methods of imparting smoke only affect the food surface, and are unable to preserve food, thus, smoking is paired with other microbial hurdles, such as chilling and packaging, to extend food shelf-life.
The smoking of food likely dates back to the paleolithic era. As caves or simple huts lacked chimneys, these dwellings would probably have become very smoky. It is supposed that early men would hang meat up to dry and out of the way of pests, thus accidentally becoming aware that meat that was stored in smoky areas acquired a different flavor, and was better preserved than meat that simply dried out. This process was later combined with pre-curing the food in salt or salty brine, resulting in a remarkably effective preservation process that was adapted and developed by numerous cultures around the world. Until the modern era, smoking was of a more "heavy duty" nature as the main goal was to preserve the food. Large quantities of salt were used in the curing process and smoking times were quite long, sometimes involving days of exposure.
The advent of modern transportation made it easier to transport food products over long distances and the need for the time and material intensive heavy salting and smoking declined. Smoking became more of a way to flavor than to preserve food. In 1939 a device called the Torry Kiln was invented at the Torry Research Station in Scotland. The kiln allowed for uniform mass-smoking and is considered the prototype for all modern large-scale commercial smokers. Although refinements in technique and advancements in technology have made smoking much easier, the basic steps involved remain essentially the same today as they were hundreds if not thousands of years ago.