Producer gas is called "gas" because it is a gaseous mixture of combustible and non-combustible gases produced from the incomplete combustion of a solid fuel, typically coal or coke.

Here's why it's classified as a gas:

* State of matter: Producer gas is a mixture of gases, meaning it exists in the gaseous phase at room temperature and pressure.

* Combustion process: The production process involves the incomplete burning of fuel, resulting in a mixture of gases that are not fully oxidized.

* Composition: It primarily consists of carbon monoxide (CO), nitrogen (N2), hydrogen (H2), and carbon dioxide (CO2), all of which are in gaseous form.

While producer gas is not a single pure gas, it's still classified as a gas due to its composition and physical state. It's important to note that producer gas is a combustible mixture, containing flammable gases like carbon monoxide and hydrogen.