Venturi Smoke Generators

To smoke meat or sausages one needs to generate smoke. That task became easier to accomplish when venturi smoke generators started to appear around 2005. First in New Zealand, then in the USA, Poland and other countries.

Imagine somebody smoking a cigarette that sits next to the partially open window in a fast travelling car. The fast moving air outside creates a vacuum next to the window and pulls smoke out of the car. The same principle is used in venturi smoke generators where the pressurized air from an aquarium air pump is injected into a container which is filled with wood chips. The lowest layer of wood chips keeps on burning producing smoke. As it burns away it turns into ash that sinks to the bottom of the hopper. Then, the layer above starts to burn. The top layers cannot ignite as they are not exposed to the fresh air which is needed for combustion. The fresh air enters through the holes at the bottom of the smoke generator.

The smoke generated rises slowly, but most of it is sucked away by the air that comes out from the aquarium air pump nozzle. The air nozzle is aimed towards the opening that leads into the smoking chamber and this is the only direction for the air and smoke to travel.

There are units for sale in New Zealand (Venturi 500, 400), Poland (Roger) or in the USA (Smoke Daddy™), and although they may differ slightly in construction details, the engine that powers them is in all cases the same: an aquarium air pump. We have tried different types of venturi smoke generators and they all worked well.

Wood chips.

A big advantage of Venturi smoke generators is that they accept different sizes of wood chips so they are not locked in to any particular brand of a smoker.

Low Nozzle Smoke Generator

This is a typical venturi smoke generator. Connecting pipe is placed low and smoke box and smokehouse are at the same level. Such an arrangement works out well with small smokers.

Low nozzle cofiguration smoke generator.

The top of the container (cover) is loosely attached, but should make a reasonably tight connection to prevent the loss of smoke. There is no bottom, the container may be placed directly on the ground. A hole is made for the pipe that connects the smoke box with the smokehouse. The connecting pipe can be considered the smoke delivery channel. This pipe may be inserted loosely, threaded on both ends and secured with nuts, threaded into the smokehouse wall and the wall of the wood burning container, etc. This will depend on your technical abilities and the fanciness of the design.

The disadvantage of this design is that larger wood chips can get lodged in on top of the pipe and prevent more chips from dropping down. This will stop the fire. For that reason the length of the pipe in a smoke box should be kept to the minimum. Secondly, the pipe’s opening must be somehow protected, otherwise wood chips may enter inside and block the intake of smoke. Thirdly, this design does not contribute to the natural draft of the smokehouses because the smokehouse and the firebox are placed at the same level. This means that when the pump is off, the system will have little power to suck the smoke up.

Those minor flaws of the above design can easily be corrected by flipping the smoke box 180° on its horizontal axis and placing it either below the smokehouse or raising the smokehouse higher. Of course the fresh air supply holes must be present in the top and the bottom of the firebox and are simply covered with tape.

The high nozzle configuration induces stronger draft, providing that the smokebox is placed below the smokehouse. Even with a pump off, there should be enough natural draft to allow a thin smoke production. The bigger height between the fresh air inlet and the smoke exhaust, the stronger the draft.

High Nozzle Smoke Generator

High nozzle smoke generator.

Straight Injector High Nozzle Smoke Generator

This is a simple but effective smoke generator. Smoke Daddy™ smoke generators operate on this principle. The air flowing through the nozzle exits about 1/4” before the connecting pipe, which is of a larger diameter. In this little air gap a sufficient vacuum is created to suck in the smoke into the connecting pipe. The heart of the system consists of 3 parts: air pump, air nozzle (metal tube) and connecting pipe. Those parts can be connected together in many different ways. They can be threaded, nut secured or permanently welded.

Straight injector high nozzle smoke generator.

The venturi principle is explained in our section dealing with Gas Burners.

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