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Phase 2 Formaldehyde ATCM materials, and are ventilated with the minimum code required amounts of outdoor air, the indoor formaldehyde concentrations are likely similar to those concentrations observed in residences built with CARB Phase 2 Formaldehyde ATCM materials (Chan et. al., 2018), which is a median of 25 pg/m3. For the occupants of these residential dwelling units, they will potentially have continuous exposure (e.g. 24 hours per day, 52 weeks per year) and assuming inhalation of 20 m3 of indoor air per day, the average 70 -year lifetime formaldehyde daily dose is 500 µg/day. This exposure represents a cancer risk of 125 per million, which is more than 12 times the CEQA cancer risk of 10 per million. Outdoor Air Ventilation Impact. Another important finding of the CNHS, was that the outdoor air ventilation rates in the homes were very low. Outdoor air ventilation is a very important factor influencing the indoor concentrations of air contaminants, as it is the primary removal mechanism of all indoor air generated air contaminants. Lower outdoor air exchange rates cause indoor generated air contaminants to accumulate to higher indoor air concentrations. Many homeowners rarely open their windows or doors for ventilation as a result of their concerns for security/safety, noise, dust, and odor concerns (Price, 2007). In the CNHS field study, 32% of the homes did not use their windows during the 24-hour Test Day, and 15% of the homes did not use their windows during the entire preceding week. Most of the homes with no window usage, were homes in the winter field session. Thus, a substantial percentage of homeowners never open their windows, especially in the winter season. The median 24-hour measurement was 0.26 ach, with a range of 0.09 ach to 5.3 ach. A total of 67% of the homes had outdoor air exchange rates below the minimum California Building Code (2001) requirement of 0.35 ach. Thus, the relatively tight envelope construction, combined with the fact that many people never open their windows for ventilation, results in homes with low outdoor air exchange rates and higher indoor air contaminant concentrations. The Magnolia at the Park project in Santa Ana is a multi -family residential project and is located close to roads with high traffic (e.g. I-5 and SR -55), and as a result has been id 75E-260 21 1z