I'm not an expert, but I found a paper that surveyed the indoor air concentration of various pollutants in homes. The lower number is mid-range of measurements,

I'm not an expert, but I found a paper that surveyed the indoor air concentration of various pollutants in homes. The lower number is mid-range of measurements, while the higher number is the upper bound. chloroform: 30–100 μg/m³ benzene: 2–10 μg/m³ A volume reference might also be handy. An 800 sq ft apartment (~80m²) with a ceiling height of 8ft (~2.5m) is ~200m³. Source: Figure 5 of "Hazard Assessment of Chemical Air Contaminants Measured in Residences" (2010) by Logue, J.M. https://cloudfront.escholarship.org/dist/prd/content/qt6gr6d738/qt6gr6d738.pdf https://cloudfront.escholarship.org/dist/prd/content/qt6gr6d...