The SIM-HG range are silent in-line mixed flow fans for duct installation, capable of various all-round ventilation purposes, including environments which require low noise ventilation. The SIM-HG range incorporates an easily removable fan body constructed from environmentally friendly material, allowing for efficient maintenance. The corrosion resistant, durable impellers are protected by a low-flammable polypropylene casing, with the addition of Japanese bearings and a backdraft damper to prevent loss of air. The fan body includes two-layer sound absorbent cotton and sound wave holes, therefore providing reducing noise. This ensures the usefulness of the SIM-HG range to a wide variety of applications, including hospitals, surgeries, libraries, and meeting rooms.