Nm³/hr stands for Normal Cubic Meters per Hour. It's a unit of measurement used to express the volumetric flow rate of a gas, typically at standard temperature and pressure (STP).  

• Normal refers to the conditions of 0°C and 1 atmosphere (101.325 kPa).  
• Cubic Meters is the unit of volume.  
• Hour is the unit of time.

Therefore, Nm³/hr represents the amount of gas (in cubic meters) that flows through a particular point in one hour, under standard conditions.  

This unit is commonly used in industries like oil and gas, chemical processing, and environmental monitoring.