AST8 Carbon/Hepa combination filter for downflow workstation. Air Science carbon filters are based on enhanced, activated carbon particle formulations from specially selected, naturally occurring raw material superior to wood or other organic sources. Our carbon is treated to attain the proper porosity and aggregate surface area and to react with several ranges of aerosolized chemicals moved through the filter by an air handling blower. Air Science Multiplex HEPA filters provide a range of high performance protection. These self-contained filters are designed to physically capture particles larger than 0.3 microns with >99.999% typical efficiency.