Many test articles are solubilized or suspended in an aqueous vehicle for aerosolization with nebulizers and other atomizing devices. This may produce larger than desired particle size distributions and increase the relative humidity in the inhalation exposure chamber or aerosol sampling system. To mitigate these phenomena, In-Tox Products developed the Quad Track Diffusion Dryer.
As the name suggests, the Quad Track Diffusion Dryer has four woven metal cloth aerosol paths that are 2.5 cm in diameter. Each aerosol path is encased in color indicating silica gel desiccant beads. The internal components are enclosed in a cylindrical body and two end caps. The end caps are custom designed to integrate with the customer’s aerosol delivery line. The Quad Track Diffusion Dryer is available in a 22.9 cm length.
Comparison tests were conducted between a single-path diffusion dryer and the Quad Track Diffusion Dryer. Filter samples collected from upstream and downstream locations demonstrated minimal impaction and sedimentation losses (less than 10.1 %) at volumetric flow rates of 5, 10, and 20 L/min. Scanning Mobility Particle Sizer samples showed that diffusion losses agreed with theoretical estimates and were less than 1% for 30 nm particles at a volumetric flow rate of 10 L/min.
Alternatively, the Quad Track Diffusion Dryer can be filled with granular activated carbon and used to adsorb organic vapors. Comparative tests demonstrated the removal of up to 96% of ethanol vapor when operated at 10 L/min. Test results are detailed in "Design and Evaluation of the Lovelace Quad-Track Diffusion Dryer".
The Quad Track Diffusion Dryer has a convenient port located on the barrel to add or remove the color indicating silica gel desiccant beads. It can also be used to check the color indicator status of the beads. Saturated color indicating silica gel desiccant beads may be recharged by heating them at approximately 120 °C for 1-2 hours
The In-Line Mixer is an aerosol conditioning device that introduces clean, compressed air into the aerosol stream in a laminar manner. As air is added, it dilutes and gently mixes the aerosol. The aqueous fraction of the test article is driven into the vapor phase resulting in a dryer, more stable aerosol.
The In-Line Mixer is an excellent choice to use in conjunction with the Quad Track Diffusion Dryer to remove the vaporized aqueous fraction and reduce the relative humidity in the system.
The Radial Mixer is an aerosol conditioning device that introduces clean, compressed air into the aerosol stream in a rotating manner. The Radial Mixer provides more mixing action than the In-Line Mixer and it also produces a dry, stable aerosol by driving the aqueous fraction of the test article into the vapor phase. To avoid turbulent flow, the Radial Mixer should not be operated at a volumetric flow rare greater than approximately 10 L/min.
The Radial Mixer may also be used with the Quad Track Diffusion Dryer to further dry the aerosol and effectively reduce relative humidity in the system by removing the vaporized aqueous fraction of the test article.