A device and methods for using a device, for determining a passing of flatus is described. The device comprises a sleeve comprising a first porous gas-permeable surface, a second surface attached to the first porous gas-permeable surface defining a pocket within the sleeve, and a flatus detector inserted within the pocket of the sleeve and positioned between the first porous gas-permeable surface and the second surface. The flatus detector may be a dry-surface carbon dioxide detector that irreversibly changes colour upon contact with increased concentrations of CO2 gas, a chemiresistor, or a near field communication tag. The chemiresistor or near field communication tag may be modified for detecting target gases. The device may be a patch that is affixed to a patient or attached to a garment that is worn by the patient, or a capsule, with a detector disposed therein.