A method and intersection testing module in a ray tracing system for determining whether a ray intersects a 3D axis-aligned box that represents a volume defined by a front-facing plane and a back-facing plane for each dimension. Scaled inverse ray components are determined and a scaled minimum culling distance is determined using a result of multiplying an unscaled minimum culling distance for the ray by a predetermined magnitude. Scaled intersection distances to the planes defining the box are determined using scaled inverse ray components. The largest of the determined scaled intersection distances to a front-facing plane of the box is identified. The smallest of the determined scaled intersection distances to a back-facing plane of the box is identified. It is determined that the ray intersects the box if all of three determinations are satisfied, and it is determined that the ray misses the box if one or more of the three determinations are not satisfied.