A person support apparatus, such as a bed, cot, stretcher, or the like, includes an exit detection system that has, in some embodiments, multiple user-selectable modes. A first mode issues an alert in response to a static condition being met and the second mode issues an alert in response to a dynamic condition being met. The static condition may be defined by an unchanging boundary that triggers an alert if the occupant's center of gravity crosses the boundary. The dynamic condition may be defined by a changing boundary that triggers an alert if the occupant's center of gravity crosses it. The changing boundary may change based upon the occupant's height, weight, BMI, vital sign, or other characteristic. The changing boundary may also change based upon a position of one or more components of the person support apparatus, such as a siderail or Fowler section.