Unburnt carbon particles are released on combustion of which type of fuel?

Incomplete combustion:

• The unburnt carbon particles are released on incomplete combustion.
• Carbon fuels such as wood, coal, and petroleum release unburnt carbon particles.
• Incomplete combustion of these fuels gives Carbon monoxide$\left(\mathrm{CO}\right)$ gas.
• Carbon monoxide is a very poisonous gas.

Thus, unburnt carbon particles are released on combustion of fuels such as wood, coal as well as petroleum.