A leak detection system for testing a single gas container comprising: a substantially sealed accumulation chamber adapted to accommodate the single gas container that has a valve and a crimp, the accumulation chamber being sealed so that when a gas container is in the chamber gas leaked from that container accumulates in the chamber, wherein the accumulation chamber is adapted to accommodate the gas container in an upside down position with the valve facing downwards, and wherein the accumulation chamber is shaped such that when the container is in the chamber a valve chamber is defined and a crimp chamber is defined; a reference gas source; an optical detector for detecting leaked gas, the detector including an optical cell and a laser configured to continuously emit laser pulses and wherein the optical detector is configured to constantly monitor the intensity of detected light; and a controller comprising a switch arranged to switch between three positions for selectively switching, in a first position, the reference gas source, in a second position, the valve chamber, and in a third position, the crimp chamber into fluid communication with the optical cell, such that when the switch is in the first position the optical cell is purged by the reference gas and wherein the system further comprises: a first sampling path between the valve chamber and the switch, a second sampling path between the crimp chamber and the switch and a third sampling path between the reference gas source and the switch, wherein the first, second and third sampling paths are independent and wherein the optical detector is operable to perform measurements as reference gas is delivered to the optical cell when the switch is in the first position and continue to perform measurements as valve chamber gas is delivered to and flows through the optical cell when the switch is switched to the second position or continue to perform measurements as the crimp chamber gas is delivered to and flows through the optical cell when the switch is switched to the third position and use the measurements of reference gas and the measurements of one of the valve chamber gas and the crimp chamber gas to provide a differential measure of leaked gas. a substantially sealed accumulation chamber adapted to accommodate the single gas container that has a valve and a crimp, the accumulation chamber being sealed so that when a gas container is in the chamber gas leaked from that container accumulates in the chamber, wherein the accumulation chamber is adapted to accommodate the gas container in an upside down position with the valve facing downwards, and wherein the accumulation chamber is shaped such that when the container is in the chamber a valve chamber is defined and a crimp chamber is defined; a reference gas source; an optical detector for detecting leaked gas, the detector including an optical cell and a laser configured to continuously emit laser pulses and wherein the optical detector is configured to constantly monitor the intensity of detected light; and a controller comprising a switch arranged to switch between three positions for selectively switching, in a first position, the reference gas source, in a second position, the valve chamber, and in a third position, the crimp chamber into fluid communication with the optical cell, such that when the switch is in the first position the optical cell is purged by the reference gas and wherein the system further comprises: a first sampling path between the valve chamber and the switch, a second sampling path between the crimp chamber and the switch and a third sampling path between the reference gas source and the switch, wherein the first, second and third sampling paths are independent and wherein the optical detector is operable to perform measurements as reference gas is delivered to the optical cell when the switch is in the first position and continue to perform measurements as valve chamber gas is delivered to and flows through the optical cell when the switch is switched to the second position or continue to perform measurements as the crimp chamber gas is delivered to and flows through the optical cell when the switch is switched to the third position and use the measurements of reference gas and the measurements of one of the valve chamber gas and the crimp chamber gas to provide a differential measure of leaked gas. a first sampling path between the valve chamber and the switch, a second sampling path between the crimp chamber and the switch and a third sampling path between the reference gas source and the switch, wherein the first, second and third sampling paths are independent and wherein the optical detector is operable to perform measurements as reference gas is delivered to the optical cell when the switch is in the first position and continue to perform measurements as valve chamber gas is delivered to and flows through the optical cell when the switch is switched to the second position or continue to perform measurements as the crimp chamber gas is delivered to and flows through the optical cell when the switch is switched to the third position and use the measurements of reference gas and the measurements of one of the valve chamber gas and the crimp chamber gas to provide a differential measure of leaked gas.