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

Air Filters - Arrestance and Efficiency

Air filters efficiency and arrestance.

Sponsored Links

The mission of an air-filter is to remove particulate or gaseous materials from the air-stream and efficiency and arrestance are used to describe filter functionality.

Air Filter Efficiency

Efficiency describes how well an air filter removes microscopic particles - such as dust, dust mites, pollen, mold, bacteria, and smoke.

In the ASHRAE 52.1 Standard test method, efficiency is a measure of ability to remove the staining portion of atmospheric dust from test air - officially termed "Atmospheric Dust Spot Efficiency".

Air filter efficiency can be expressed as

μe = nt / nu = (nu - nd) / nu                                  (1)


μe = air filter efficiency

nt = particles trapped

nu = particles upstream

nd = particles downstream

Air Filter Arrestance

Arrestance is a measure of the ability of an air filtration device to remove synthetic dust from the air.

The arrestance describes how well an air filter removes larger particles - such as dirt, lint, hair, and dust. ASHRAE arrestance is a measure of the ability of a device to remove ASHRAE dust from test air.

The dust holding capacity of a filter is the amount by weight of standard dust the filter will hold without exceeding the resistance 0.18 in W.G. for low-resistance filters or 0.50 in W.G. for medium-resistance filters and 1.0 in W.G. for high-resistance filters.

Filter dust arrestance can be expressed as

μa = 1 - Ca / Cb                                     (2)


μa = dust arrestance

Ca = dust concentration after filter

Cb = dust concentration before filter

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, (2005). Air Filters - Arrestance and Efficiency. [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