Engineering ToolBox - Resources, Tools and Basic Information for Engineering and Design of Technical Applications!

Duct Systems - Pressure Classifications

Duct systems are commonly divided into three pressure classifications.

Sponsored Links

Duct systems are often divided into three pressure classifications:

  • Low Pressure Systems - where fan static pressures are less than 3 in WC (750 Pa) and duct velocities in general less than 1500 fpm (7.5 m/s)
  • Medium Pressure Systems - where fan static pressures are in the range 3 to 6 in WC (750 - 1500 Pa) and duct velocities in general less than 2500 fpm (12.5 m/s)
  • High Pressure Systems - where fan static pressures are in the range 6 to 10 in WC (1500 - 2500 Pa) and duct velocities in general less than 4000 fpm (20 m/s)

Medium pressure classification is commonly used for primary main ductwork like fan connections, risers and main distribution.

Low pressure classification should be used for secondary ductwork like runouts and branches from main ducts to end terminals.

Sponsored Links

Related Topics

Related Documents

Sponsored Links

Engineering ToolBox - SketchUp Extension - Online 3D modeling!

3D Engineering ToolBox Extension to SketchUp - add parametric components to your SketchUp model

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro .Add the Engineering ToolBox extension to your SketchUp from the SketchUp Pro Sketchup Extension Warehouse!

About the Engineering ToolBox!


We don't collect information from our users. Only emails and answers are saved in our archive. Cookies are only used in the browser to improve user experience.

Some of our calculators and applications let you save application data to your local computer. These applications will - due to browser restrictions - send data between your browser and our server. We don't save this data.

Google use cookies for serving our ads and handling visitor statistics. Please read Google Privacy & Terms for more information about how you can control adserving and the information collected.

AddThis use cookies for handling links to social media. Please read AddThis Privacy for more information.


This page can be cited as

  • Engineering ToolBox, (2018). Duct Systems - Pressure Classifications. [online] Available at: [Accessed Day Mo. Year].

Modify access date.

. .


3D Engineering ToolBox - draw and model technical applications! 2D Engineering ToolBox - create and share online diagram drawing templates! Engineering ToolBox Apps - mobile online and offline engineering applications!

Scientific Online Calculator

Scientific Calculator

3 10

Sponsored Links