What is natural draft?

Natural draft refers to the movement of air caused by differences in temperature and density within a space or system. In this context, warmer air rises because it is less dense, creating a pressure difference that draws in cooler, denser air from outside. This phenomenon is a fundamental principle used in various systems, such as chimneys and flues, to ventilate gases or maintain airflow without any mechanical assistance.

When comparing this understanding to the other types of drafts mentioned, it's clear that they involve different mechanisms. A mechanical ventilation system relies on fans or blowers to move air, which is distinct from natural draft's reliance on thermodynamic principles. A forced draft also depends on mechanical means to push air into a space, contrary to the passive nature of natural draft. Additionally, electrically driven exhaust systems use electrical power to expel air or gases from a space, further illustrating that these options fundamentally differ from the natural process described in the correct answer.