The difference between NM3 and M3 lies in the conditions under which the volume is measured: M3 (Cubic Meter): This is a standard unit of volume in the International System of Units (SI) and is used to measure the volume of a three-dimensional space. The volume of solids, liquids, and gases is represented by M3, regardless of the temperature and pressure conditions.
NM3 (Normal Cubic Meter): This is a measurement of gas volume at standard temperature and pressure conditions. NM3 is a standard value that remains constant for a particular compound, while the value of M3 changes with varying temperature and pressure conditions. NM3 is generally used as a reference and is rarely of importance in working conditions, whereas M3 has more practical applications. In summary, M3 represents the volume of matter under any given temperature and pressure, while NM3 represents the volume of matter under standard conditions (usually 0°C and 1.01325 bar).