Smoke control systems among the most complicated building environmental systems and they also complicate our industry’s energy conservation goals. Most building occupants are unaware of the air pressure differences between, say; a corridor and a classroom; and the energy consumption of rotating machinery needed to maintain appropriate air pressure differences in a building. If a room, or a part of a building suddenly becomes “drafty” or too warm, it is frequently due to a problem with the fire protection system. Pressure differentials are even more complicated in healthcare settings. The cost of building and maintaining the delicate air pressure balance among fire safety, human comfort and energy conservation concepts is non-trivial; perhaps up to as much as 10 percent of a building’s annual operation and maintenance.