The condition of gas as it presents itself in the pipeline is often not ideal for accurate measurement, by an orifice flow meter. It is the requirement of the American Gas Association (AGA) that the natural gas be in a single phase and with a swirl-free fully developed profile as it passes across the orifice plate to meet the standard of measurement to provide acceptable uncertainty for the flow calculation. Thus it is often necessary to “condition” the gas prior to measurement. Using the basic laws of gases we can control these conditions by altering the temperature, pressure, or component makeup of the gas. Neglecting these conditions will create a poor measurement environment and inaccurate measurement. It is therefore necessary for measurement personnel to be familiar with common production equipment, how that equipment is utilized and what effect it can have on the overall ability for a system to provide accurate measurement.