Which of the following is one of the mechanical ventilation systems?

The correct answer, which pertains to mechanical ventilation systems, is the choice that includes mechanical air intake and mechanical exhaust. This type of ventilation actively uses fans and blowers to circulate air in and out of a space, helping to control indoor air quality, temperature, and humidity.

Mechanical ventilation is important for maintaining desirable air conditions, particularly in areas where natural airflow is insufficient or where contaminants need to be controlled effectively. By using powered systems, it ensures a consistent exchange of air that is necessary for safety and comfort, especially in tightly sealed buildings.

Natural draft relies solely on differences in temperature and pressure to move air, which is not powered mechanically. Passive ventilation takes advantage of prevailing winds and natural buoyancy but does not involve any mechanical systems either. Cross ventilation utilizes openings on opposite sides of a space to promote airflow but again does not require any mechanical components. Therefore, the inclusion of mechanical systems in the correct answer differentiates it from the other options, which rely on natural or passive means of air movement.