2001-02 Lawrence Berkeley National Laboratory (LBNL) nested, crossover-design study explored operating profiles of two mechanical ventilation (HVAC) systems (alternated over a period of approximately nine weeks during 2001 Fall school semester) in pairs of classrooms sited adjacent to one another, equipped with either standard or alternate (low-emissivity) interior finish materials. Our retrospective analysis included inferring estimated indoor ozone concentrations. Because ozone can react with certain indoor pollutants to generate secondary organic aerosols, a mass-balanced based indoor/outdoor ratio expression was used to model indoor ozone to subsequently model indoor particles from possible ozone-initiated chemistry. When IDEC HVAC is running, surface (especially ceiling) reactions dominated ozone loss processes. When standard Bard HVAC system is running, damper setting and ventilation and/or gas phase reactions accounted for most indoor-outdoor ozone difference.