In 1990, the U.S. Army asked TSI to develop an advanced-technology light scattering photometer to replace aging instruments incapable of measuring the high protection factors provided by newer gas mask designs. The result was the Model 8587 Laser Photometer, which is still in service. The U.S. Army and other photometer owners asked TSI to develop a modern version of the 8587 Laser Photometer that retains data continuity with the original version. Without data continuity, vast amounts of legacy research would not be directly comparable to new research. The result was the Model 8587A. The Model 8587A can also be used in HEPA filter scanning systems to measure the penetration efficiencies of large, high-efficiency filter assemblies.