Shown on this slide is a graph of air flow performance. Static pressure is used to evaluate the amount of impact various ventilation system components have on the air flow path within a given system. Fans create positive static pressure to move air through a given system while all other components create negative static pressure that causes resistance to air moving through a system. The positive static pressure created by fans equals the negative static pressure created by resistance as air navigates obstacles in the ventilation path. The line on the graph represents a typical axial fan performance. It can be seen in the graph that as pressure increases, the rate of air flow decreases. Standard atmospheric pressure is 100 kPa or 10.2 mm-H20.