Which option is not considered a type of oil burner?

Atmospheric burners are not typically categorized as oil burners because they primarily rely on the natural flow of air for combustion rather than a forced mechanism. Oil burners are designed specifically to use oil as a fuel source and require a delivery system for the oil, along with a means to create a controlled combustion environment.

In contrast, pressure burners, gun-type burners, and mechanical burners all integrate specific systems that help ensure the efficient and effective burning of oil. Pressure burners utilize pressurized oil to atomize the fuel for a better burn, gun-type burners are designed to project a fine spray of fuel into the combustion chamber, and mechanical burners often include a fuel delivery mechanism that enhances combustion efficiency. Thus, the distinction lies in the operational principles and the intended fuel type.