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Formula: Nm3; Cubic meter: m3. We know that gases are compressible, and their volume changes depending on pressure and temperature conditions. To facilitate comparison and measurement, it is necessary to convert the volume of gases at different pressures and temperatures into volumes at the same pressure and temperature. In other words, the volume of a gas must be measured under the same pressure and temperature conditions. These same pressure and temperature conditions are referred to as standard conditions. Currently, the standard pressure and temperature conditions adopted domestically and internationally are not unified, and this must be taken into account when using them. For the pressure condition under standard conditions, the standard atmospheric pressure is used both domestically and internationally, namely 101.325 kPa. However, the temperature condition varies: one option is to use 0°C, and under this condition, a volume of 1 m3 of gas is referred to as 1 standard cubic meter, abbreviated as 1 m³ std. Write it as 1 N m3 or 1 m3. The design and operation management departments for urban gas (including natural gas) in our country generally adopt this standard condition. For example, the \"Code for Design of Town Gas Systems\" (GB 50028-93) specifies that the measurement conditions for gas volumetric flow rate are 0°C and 101.325 kPa. Another option is to use 20°C or 60°F (15.6°C). To distinguish it from the previous standard state, the volume of 1 m3 of gas measured under this condition is referred to as 1 standard cubic meter, abbreviated as 1 base cubic meter or 1 cubic meter, denoted as 1m3. China’s petroleum and natural gas industry uses 20°C as the standard temperature; for example, the \"Standard orifice plate method for measuring natural gas flow rate\" (SY/T613-1996) specifies that the measurement conditions for natural gas volume flow rate are 20°C and 101.325 kPa. Countries such as the UK and the US, on the other hand, mostly use the imperial unit of 15.6°C, which is usually denoted as 1 Std m3 or 1 m3. The conversion relationship between them is: 1 m3 (20°C) = 0.985 m3 (15.6°C) = 0.932 m3 (0°C). Based on the above explanation, in our chemical production, 1 Nm3 = 1 m3, which refers to the volume of a gas at 20°C and 101.325 kPa.