Continuous Positive-Pressure Ventilation (PPV) Sample Clauses

Continuous Positive-Pressure Ventilation (PPV). Vapor intrusion primarily occurs when there is a lower pressure inside the building, i.e., causing soil gas to flow into a building through cracks in the floor (U.S. EPA, 2002b). As such, the vapor intrusion process may be mitigated by creating a positive pressure (i.e., a pressure slightly higher than the outside air pressure) inside the building. When there is a positive pressure inside a building, air inside the building will flow outward through any cracks in the floor, i.e., toward the lower outdoor pressure. The U.S. EPA recognizes this in its vapor intrusion guidance, indicating: “A building may be positively pressurized as an inherent design of the heating, ventilation, and air conditioning system. It may be possible to show that the [vapor intrusion] pathway, in this case, is incomplete, at the current time, by demonstrating a significant pressure differential from the building to the atmosphere.” (U.S. EPA, 2002b) Similarly, the California Building Code (“CBC”), Section 1202.2.7, requires positive pressure ventilation in ticket booths and other occupied spaces inside of parking garages. The purpose in that case is to prevent fumes from the parking garage from entering those spaces, i.e., to mitigate vapor intrusion from the parking garage into those occupied spaces.