Minimizing Smoke
The key to minimizing smoke and operating the stove at high efficiency is to establish and maintain a strong draft in the chimney and control incoming air. The hot gas released from the wood is what actually burns in a fire and needs to be mixed with enough air to allow as complete burning as possible. It is possible to have too much air. The hot gas can move up the chimney too fast for complete combustion. Restricting the air supply can also create turbulence that helps mix air and hot gas. The combustion air is drawn into the fire chamber by the amount of the chimney draft. Anything that lowers the temperature of the gas in the fire chamber or chimney will decrease the speed of the gas moving up the chimney, reducing the draft, and will cause excessive smoke. Smoke is unburned fuel and is wasted if it is not burned. It is also a hazard to people who breathe it in.
Start the fire small, with paper in the middle, small sticks on top, and a few larger sticks (about one-half inch diameter or less) on top of that. Once the fire starts burning, gradually add more wood. Let the wood begin burning before adding more. Wood will decrease the temperature of the fire chamber when it is first added, until it starts burning. Adding wood slowly causes less of a drop in temperature, therefore less smoke. The same is true when pushing in wood as it burns. Don’t push all the wood in at once. Push a few in, wait a little, and then push in some more. Smaller pieces of wood burn more efficiently than large ones. It is much better to use three one-inch diameter pieces than one three-inch log. The wood needs to be dry for best results. Water stored in the wood has to be boiled to steam before the wood can get hot enough to burn.
Check the fire frequently, at least every five minutes. Push the wood in as needed, several pieces at a time. Heat is what causes the strong chimney draft. If the wood is allowed to burn down too far the draft will drop and the stove will smoke.
When the fire has been started and is burning cleanly, add the cook pot with some liquid in it. The cook pot should never be heated empty. The pot could be damaged. The pot will drop the temperature of the gas from the chimney until it has warmed up. Adding liquid to the pot in stages instead of putting it in all at once will help minimize smoke.
The stove does not have to be run at maximum capacity. It gives a lot of heat, but lowers the efficiency. It may also warp or shorten the life of the stove pipe and heat chamber. With some experience, the operator should be able to plan about the amount of heat needed and the amount of time before the food being cooked needs less heat, and can cut back on the amount of wood being added, or pull back some of the wood already in the fire. There will be some minimum amount of fire needed to keep the stove burning with low smoke. This amount will also need to be determined by experience.
Operating a “rocket” stove with minimal smoke depends on the diligence of the operator. A carefully tended fire will put out maximum heat with minimum smoke.