Unlike liquids, gases can be compressed. The volume changes when the temperature and/or the pressure change. When specifying a gas volume, the reference temperature and the reference pressure must thus also always be specified. The flow unit is than referred to as normalized (f.i. ln/min) or standardized flow (f.i. ls/min)
When we refer to “Normal” flow we in general use:
Temperature Tn = 273,15 K, corresponds to 0 °C
Pressure Pn = 1013,25 mbar abs
When we refer to “Standard” flow we in general use:
Temperature Tn = 293,15 K, corresponds to 20 °C
Pressure Pn = 1013,25 mbar abs
See also: http://de.wikipedia.org/wiki/Standard conditions
Please note: Not everyone understands standard conditions in the same way. In the case of reference pressure, everyone agrees, but in the case of reference temperature, there are differences:
Gas suppliers in Europe do not use 0 °C, but 15 °C as their “Normal condition”
To avoid misunderstandings, the reference conditions are specified clearly in our correspondence.
On request, we also deliver the devices with another reference temperature.
