Nm³/h and m³/h both describe gas flow rates, but they use different reference conditions.

Nm³/h refers to gas volume at 0°C and 1013 hPa, while m³/h (standard m³/h) uses 20°C and 1000 hPa. Because the temperature and pressure differ, the values are not interchangeable. Industries choose one unit depending on their standards, so it is important to always specify the reference conditions to ensure correct comparison and accurate measurement.