The Axial Flow Large-Scale HEPA Filter Test Stand (ALSTS) is designed to evaluate the performance of axial flow nuclear-grade HEPA filters with flow rates up to 1500 cubic feet per minute, temperatures up to 170 °F, and humidities up to 90%. The ALSTS allows for the introduction of various aerosols and consists of three main sections. The upstream section draws outside air from square ducting and uses an electric heater and steam injection to control airstream conditions. Aerosol generators are also used upstream to inject various aerosols into the air for loading and filter efficiency measurements; the upstream section contains additional sensors that measure aerosol flow and concentration upstream of the filter. The ALSTS filter housing is centrally located on the test stand and holds the test filter; the filter housing also retains additional ports for sampling probes and cameras for visual observation. The downstream section uses a fan to pull air from the filter housing and is configured to sample aerosol flow and concentration downstream of the filter.