Wood burns with a visible flame due to the flammable gases produced during combustion, which react with oxygen. In contrast, coal can produce a small flame, but it is less pronounced than wood. When burning coke or charcoal, there is typically no visible flame because these materials are primarily composed of carbon, which does not generate flammable gases. Poor ventilation during charcoal burning can lead to the production of carbon monoxide, which is hazardous but does not support a flame. The discussion highlights the differences in combustion properties between wood, coal, and charcoal. The thread has been locked due to inactivity.