Rate of Spread (ROS) 2
Rate of Spread (ROS) 2 : A fire behavior term used to express relative horizontal growth of a wildland fire. The relative activity of a fire in extending its horizontal dimensions. It can be expressed as a rate of increase for the total perimeter of the fire, as a rate of forward-spread for the fire front, or as a rate of increase in area. It is usually expressed as a rate in chains or acres per hour. Expressed in total perimeter growth in chains per hour