Abstract: A method and detection system for determining volumetric parameters of liquid within a container using the diffusion of a reference amount of gas are described The method includes filling a first tube with gas to a reference pressure, allowing the gas to diffuse to the container, and measuring a first stable pressure of the gas. The container is then filled with an amount of the liquid and the first tube is filled with gas to the reference pressure. The supply of gas diffuses to the container and a second stable pressure of the gas is measured. Then, a portion of the amount of the liquid is discharged from the container and the first tube is filled with gas to the reference pressure. The supply of gas diffuses to the container, an instantaneous pressure of the supply of gas is detected, and an instantaneous volume of the liquid within the container is calculated.