Our project is an office building undergoing major renovation. The building will remain operational while the renovation is ongoing. The building occupancy will be phased to move the employees between various floors, as required, while keeping the relevant floor undergoing construction as unoccupied. The office building has a central atrium with open office spaces at its periphery looking into the atrium without any physical air barrier.

My questions are-
1. As the individual floors are planned to be occupied immediately after the floor-level renovation, can we do a separate flush-out for each floor ?
2. If yes then, since the building will remain occupied throughout the construction stage, in such a case even if "during occupancy" option is selected, how effective is that flush out process going to be for individual floors as the atrium allows for the leakage of contaminants to other floors?

Thanks in advance for your responses!