Gas flow can be measured by mass or by volume. Same amount of gas will be a different volume depending on both the temperature and the pressure. There are many definitions and standards trying to pin down the "right" reference conditions, often denoted by N- or S- prefix before the volumetric unit. These reference conditions vary depending of issuer, industry, region, instrument manufacturer, and even with time (when the authors redefine).

With volumetric measurements, the dissonance between the definition of NTP or STP, as well as the dynamic nature of actual condition are recurring sources of error.

Flowseg allows flows in: g/min, which is always the same regardless of conditions, as well as any reference condition for volumetric units. The volumetric flow is either in ml/m (milliliters per minute) or in ccm (cubic centimeter per minute) as these units are interchangeable, and this is freely selectable per user preference.

The unit name and the reference conditions can be pre-defined from the drop-down menu, or entered by hand. Software does not provide definitions for accronyms NTP or STP but users are free to use them as befits their needs, as well as custom reference conditions usch as in laboratories at high altitudes and low ambient pressure.