What is the main characteristic of refinery gases?

Refinery gases are primarily characterized by their use as bottled gas, which includes gases such as propane and butane. These gases are light hydrocarbons that can be easily liquefied under pressure, allowing them to be stored and transported in gas cylinders. This characteristic makes them convenient for various applications, including cooking, heating, and as fuel for certain vehicles.

The other options do not accurately represent the nature of refinery gases. They are not solid at room temperature, instead being gases; they are generally lighter than air, which influences their behavior when released; and they do not have a distinctive blue color, as many gases lack color altogether. Thus, the unique property of refinery gases being utilized as bottled gas is what sets them apart from the other inaccurate descriptions.