The Inclined Tube Air Flow Indicator (ITAFI) eliminates the alarm problem and provide a reliable indication to the operating personnel by simply observing the position of the round sphere.  The round sphere will be at the end of the tube inside the room under negative pressure OR outside the room to the other end if it is under positive pressure.  The direction of the air flow is the same as the position of the round sphere. When the round sphere is in the horizontal position the pressure differential is at zero with no flow direction.