The paper gives results of a determination of the relative effectiveness of local versus central control through the heating, ventilating, and air conditioning (HVAC) system. Since many sources cannot be removed from indoors, it is important to know the impact of the source in the room, as well as in the building as a whole. The decrease in contamination resulting from source venting, in-room air cleaners, increased ventilation from the HVAC, and air cleaners in the HVAC system was examined. The Indoor Air Quality Simulator for Personal Computers (IAQPC) was used to study a variety of the options available in a building with an HVAC system. A building layout and a steady source were chosen. The time-dependent concentrations in the building were determined. The air cleaning options tested were (1) increased ventilation through the HVAC system and (2) in-room and HVAC system air cleaners. The reductions in concentrations for the building as a whole and for source and nonsource rooms are reported.