If you smoke regularly, it is the problem of the stove; If there is occasional smoke, or the chimney is not well built, the outside wind will blow into the chimney, causing the smoke to flow back, and in serious cases, the fire will be ejected from the oven door. In short, it is a technical problem of making a stove. The smoke-free principle at the entrance of the stove is very simple, and the construction details are very complicated. Master Ding has many technical data and successful cases of saving firewood stoves.