Indoor Air sciences CSMI Practice Exam

What is required to create positive pressure in a building?

1. Exhaust more air than supply

2. Return more air than supply

3. Have an air tight building

4. Supply more outdoor air than exhaust

The correct answer is: Supply more outdoor air than exhaust

To create positive pressure in a building, it is essential to supply more outdoor air than is exhausted from the building. This approach ensures that the amount of air being introduced into the indoor environment surpasses the amount being removed, leading to an overall increase in the internal air pressure relative to the outside atmosphere. Consequently, the building will have a greater tendency to push air out through any openings, which helps in preventing the infiltration of outdoor pollutants and allergens. In contrast, if more air is exhausted than supplied, or if the return air exceeds supply, the building will experience negative pressure, which can lead to drafts, unconditioned air entering the building, and potential air quality issues. An airtight building, while beneficial for energy efficiency, does not by itself create positive pressure unless the air supply exceeds exhaust. Thus, supplying more outdoor air is crucial for maintaining that desired positive pressure within a structure.