Regularly gases are measured based on its volume per hour and there are some types of devices to do it. Usually, measurement units in these cases are SCFH and Nm3/h. Most processes are designed and set based on these units.
As a chemical process engineer, you need to make surge that those measurement units fits your heat and material balance. I mean, volume flow depends on pressure and temperature. So any time you see “S” or “N” as a prefix to flow measurement confirm what is their basis.
For instance, Standard US is based on 101,325 kPa @ 15.55 C, Standard ISO 101,325 kPa @ 15C and Standard AGA 101,560 kPa @ 15.55 C. In the other hand, Standard (Normal) International is based on 101,325 kPa @ 0 C. Not to mention natural gas industry that uses 20 C as temperature basis.
Taking into account that PV=nRT, the wrong temperature assumption can result in approx 6% error in your flow measurement.
That may impact your process design and worse than that you may not guarantee a Customer requirement.
Some tips I would share with you to avoid this problem is to verify Customer’s contract definition, ask for Supplier clarification, inform instrumentation guy the correct P and T basis of the project.
