3D Blast is a computer program that provides quick calculations and visualization of the effects of an open-air explosion on different building geometries. In general, it allows the user to approximate the three-dimensional blast load engulfment of a structure without having to resort to complex analyses. Given the building dimensions and the size and location of an explosive charge, the program will estimate the pressure and impulse distribution over the exterior of the building. The range to each node on the 3-D model is determined using the shortest path around the exterior of the facility. The software then uses an airblast driver to determine the appropriate pressure and impulse magnitudes for the range and orientation of each element. The resulting pressure and impulse engulfment are plotted as contours on the building model. The blast load calculation procedure outlined in the Army Technical Manual TM 5-855-1, “Fundamentals of Protective Design for Conventional Weapons” is the basis of the estimates performed by the program.