Propane is a colourless gas that burns. People use it for cooking and heating. It is often stored as a liquid in a metal bottle or tank; when you open the valve it turns back into gas and feeds a stove or a heater. You cannot see it, and in its pure form it has little smell, so companies add a strong smell so a leak is obvious. It is both a chemistry-class word and a shop word. Though actually, in daily life in Taiwan people often just say 瓦斯 for the bottled gas at home, which may be propane, butane, or a mix — they are not picking the chemical name. Propane is the precise name for this one gas. It is not the same thing as petrol, and it is not “gas” in the American sense of car fuel. Used with care it cooks dinner; if it collects in a closed room and meets a spark, it can explode.