Vapor intrusion is the process by which harmful chemicals vaporize and enter homes and businesses through cracks in the foundation or other openings. These chemicals can come from a variety of sources, including dry cleaners, gas stations, and factories. Once inside, they can build up to dangerous levels, posing a serious health risk to occupants. Vapor intrusion can be difficult to detect, as it often occurs without any noticeable odor or sign. However, long-term exposure to vapor intrusion can lead to a variety of health problems, including cancer, liver damage, and respiratory problems. Vapor Intrusion mitigation may be installed in new or existing. construction and is now being required in many commercial pre- construction plans.The intent of vapor intrusion mitigation measures is to stop vapor-bearing soils or groundwater from entering buildings, or to vent any vapor that does enter the building to the outdoors before it can reach indoor air spaces. There are several types of vapor intrusion mitigation measures that can be employed, depending on the needs of the project. These include sealing openings, installing vapor barriers, and passive venting. Each of these methods can help to prevent vapor intrusion and keep indoor air clean.