M2 Commercial Mechanical Inspector Practice Exam 2025 – Complete Prep Guide

The type of air typically supplied from outside to improve indoor air quality is fresh air. Fresh air refers to outside air that is brought into a building to augment the existing air inside. This process is crucial for diluting indoor air pollutants, replenishing oxygen levels, and enhancing overall air quality. Fresh air helps to reduce the concentration of contaminants that can accumulate indoors due to inadequate ventilation, human activity, or the use of chemicals in cleaning and maintenance.

Conditioned air, while essential for maintaining comfort, usually refers to air that has been treated for temperature and humidity but does not necessarily originate from outside; it can be recirculated air that has undergone processing. Exhaust air is air that is removed from the building, typically to expel pollutants and moisture, and return air is the air that is cycled back into the heating and cooling system after it has circulated through the space, typically not from the outside. Thus, fresh air is specifically intended to enhance indoor air quality by directly introducing clean, outside air to the indoor environment.