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Gauge & Absolute Pressures

For the majority of fan selections you will work with gauge pressures.

Gauge pressures are pressures relative to atmospheric conditions and are usually given as positive and/or negative values by the system designer.

Absolute pressures are relative to a perfect vacuum (ie zero absolute is a perfect vacuum). It is therefore not possible to have a negative absolute pressure.

The absolute pressure at mean seal level is 101.325 KPa (1013.25 millibar). Some system designers will specify the fan pressures in absolute terms. Generally you will be able to tell whether the pressures are gauge or absolute values by their magnitude.

Note that if you select gauge pressures the corresponding absolute values change automatically as you type them in. Conversely if you select Absolute Pressures the gauge pressures will change automatically.