When calculating the compressed air flow rate, we need to take temperature and pressure factors into account, as air is compressible. The actual volume of a constant number of moles of gas depends on the measurements of temperature and pressure. Higher the pressure, smaller the volume Higher the temperature, bigger the volume Therefore, we can use the reference temperature and pressure conditions to specify the volume of gas measured under those conditions. Once the volume is calculated, we can convert the calculated amount into a number of moles or mass of gas.