A Total Human Exposure Model (THEM) has been developed that calculates 24-hour exposure profiles using real human activity patterns and indoor air models derived from actual measurements of pollutants. THEM was designed for implementation on personal computers. These data include diaries of over 1700 adults and children that contain coded information on locations and activities. The diary codes correspond to locations in factories, offices, restaurants and homes (room specific) and activities such as cooking, cleaning and being in the presence of a smoker. THEM determines RSP exposure by taking the location and activity information from the CAP data and assigning RSP levels for (1) Environmental Tobacco Smoke (ETS), (2) cooking, (3) cleaning, and (4) ambient levels (from motor vehicles and wood smoke). Actual RSP levels are obtained from real microenvironmental measurements conducted recently in over 300 locations. For ambient data, actual hourly diurnal particulate measurements are obtained from a continuous monitoring instrument. THEM computes RSP exposures from ETS using validated models based on the mass balance equation. Source strengths, smoking rates, room air exchange rates and room volumes are incorporated into the model by randomly sampling from actual distributions of data.