Understanding building occupancy is important for protecting public health when there is a known risk of indoor air contamination caused by vapor intrusion. Collecting information about the individuals present at a building is referred to as collecting “demographics.” The demographic information can identify if any sensitive populations spend a meaningful amount of time in the building. Sensitive populations may be at an increased risk of adverse short-term (i.e., acute) health effects and primarily include people who are:

• Under age 15
• Currently pregnant or may become pregnant
• Elderly

Risk of indoor air contamination is identified by an exceedance of the indoor air vapor action level (VAL) and/or sub-slab vapor risk screening level (VRSL) for a specific contaminant. When a VAL or VRSL is exceeded, the DNR recommends that the responsible party or their environmental consultant quickly share if any sensitive populations are present in the building. When sharing information with the DNR, the information should be general in nature, indicating whether a sensitive population is present; it should not include personal information such as names, specific ages, personal addresses and individual occupancy habits (e.g., work hours).

When there is a known exceedance of the indoor air vapor action level (VAL) and/or sub-slab vapor risk screening level (VRSL), DNR collaborates with DHS and local health who provide health-based recommendations that consider building occupancy when advising on the health risk, a timeline for a response and the need for immediate or interim actions (Wis. Admin. Code §§ NR 708.05 and 708.11.)

For more information about the risk of contaminated vapor within a building, visit dnr.wi.gov and search “vapor intrusion.”