Gas.
It is a combination of solids and gases.
Neither. It's a vapor (gas).
There are a number of examples of solid in gas solutions, such as smoke, in which carbon and air are in the form of a solution. Automobile exhaust is another example of solid in gas solution. An example of such solution is Iodine vapors in the air.
Exhaust is primarily a gas, consisting of various combustion byproducts released from an engine or other combustion processes. It typically includes carbon dioxide, water vapor, nitrogen oxides, and other pollutants. While exhaust can contain small amounts of solid particles (like soot) and liquid (such as unburned fuel or oil), its main component is gaseous.
Exhaust of an engine is a gas.
carbon monoxide is in exhaust gas
Solid
Exhaust gas pipes are silver and are made of metal.
a feather is a solid
inboard gas engine exhaust
exhaust gas
the spent exhaust gas goes out the exhaust