The DIFFUSION DRYER - DD 1448B is one of the instruments to dry wet aerosol. It consists of two parts. One is a water trap that eliminates large water droplets. The other one is a desiccant dryer it has two concentric tubes formed by a porous inner tube and an acrylic outer tube. And silica gel is contained in an annular space between two concentric tubes. The silica gel can easily regenerate using an oven with 120 ℃. Additionally, the silica gel may be replaced by other desiccants such as activated charcoal or sodium aluminosilicate.