The picture below shows how a hot balloon works.

The picture illustrates the basic structure of a hot balloon and how it is operated to soar into the air. Overall, a hot balloon has three main parts: the basket, the burner and the envelop. The way it works could be explained by the movement of two flows of hot and cool air. To begin with, the bottom part of the hot balloon is the basket for carrying passengers. Propane containing two cylinder tubes are hidden inside the basket and connected with a burner to light fire. Attached to the basket with the ropes is an envelope which shape resembles a huge balloon. A layer of skirt is coated at the bottom of the envelop. There are many lines of vertical gores on the envelop, each of which is split into rectangular panels. The envelop also has a round piece of parachute valve sealed at its top. An air balloon works by heating up the air inside its envelop. The propane tubes are the source to produce flame. Because the hot air is lighter, it would replace the cool air above it and create a strong force enough to push the balloon higher. The parachute valve then controls the hot air to escape steadily.