Gas sensing system and method

Systems and methods for sensing gas are isclosed. In one aspect, a system to monitor an output of a gas source comprises a chamber (110) comprising a plurality of input ports (112) to receive inputs from a plurality of gas sources (130), and means (116) for repeatedly blocking one of the plurality of input ports (112) for a period of time, detecting which one of the plurality of input ports (112) is blocked, collecting data from a plurality of samples from the chamber (110) while the one of the plurality of input ports (112) is blocked, and storing the data in a memory in association with an indicator of which one of the plurality of input ports (112) is blocked. Means for blocking the inputs ports can be a ball (116) rolling onto a sloped surface (114) and wherein an input port (112) is positioned on the lowest position of the sloped surface (116). Due to movements of the chamber (110), the ball (116) moves along a random path, resulting in a pseudo-random sampling of the plurality of gas sources.