What condition leads to positive pressurization in a building?

Positive pressurization in a building occurs when more air is delivered into the indoor environment than is exhausted or allowed to escape. This situation results in an increase in the indoor air pressure relative to the outside atmosphere. The excess air creates a pressure differential that can help to prevent outside contaminants, such as pollutants or allergens, from entering the building.

This is particularly relevant in environments where maintaining air quality is crucial, such as healthcare facilities or clean rooms. In these cases, ensuring that the inflow of air exceeds the outflow helps maintain a controlled and safe environment.

The other conditions do not lead to positive pressurization. For instance, if an equal amount of air is delivered and exhausted, the pressure within the building would remain neutral, rather than becoming positively pressurized. Similarly, if more air were expelled than delivered, it would create a negative pressure situation, allowing outside air to infiltrate through any openings in the building envelope. Air filtration and recycling techniques are essential for maintaining indoor air quality but do not directly influence whether a building is positively or negatively pressurized on their own.