A system comprising: - a nasal cannula comprising a flexible tube configured to transmit oxygen gas; and an optical fiber configured to transmit light having a frequency spectrum range at least including that of light resulting from combustion of the flexible tube while transmitting the oxygen gas, wherein the optical fiber is covered or coated in a substantially opaque material to prevent light from entering the optical fiber in the absence of a breach; - a detector operatively coupled to the optical fiber and configured to detect the light transmitted through the optical fiber; and - a valve configured to be actuated to interrupt the transmission of the oxygen gas through the nasal cannula in response to a signal from the detector. - a controller operatively coupled to the detector and configured to: detect an occurrence of the combustion of the nasal cannula, while transmitting the oxygen gas, based on an analysis of detected light; and send, based on the detected occurrence, the signal to the valve to interrupt the transmission of the oxygen gas through the nasal cannula characterised in that the system further comprises - an additional detector having a wavelength range sensitivity different from the detector, and wherein the controller is further configured to determine a ratio of values obtained from the detector and the additional detector to discriminate the combustion of the nasal cannula from spectra of standard light sources or normal ambient light. - a nasal cannula comprising a flexible tube configured to transmit oxygen gas; and an optical fiber configured to transmit light having a frequency spectrum range at least including that of light resulting from combustion of the flexible tube while transmitting the oxygen gas, wherein the optical fiber is covered or coated in a substantially opaque material to prevent light from entering the optical fiber in the absence of a breach; - a detector operatively coupled to the optical fiber and configured to detect the light transmitted through the optical fiber; and - a valve configured to be actuated to interrupt the transmission of the oxygen gas through the nasal cannula in response to a signal from the detector. - a controller operatively coupled to the detector and configured to: detect an occurrence of the combustion of the nasal cannula, while transmitting the oxygen gas, based on an analysis of detected light; and send, based on the detected occurrence, the signal to the valve to interrupt the transmission of the oxygen gas through the nasal cannula characterised in that the system further comprises detect an occurrence of the combustion of the nasal cannula, while transmitting the oxygen gas, based on an analysis of detected light; and send, based on the detected occurrence, the signal to the valve to interrupt the transmission of the oxygen gas through the nasal cannula characterised in that the system further comprises - an additional detector having a wavelength range sensitivity different from the detector, and wherein the controller is further configured to determine a ratio of values obtained from the detector and the additional detector to discriminate the combustion of the nasal cannula from spectra of standard light sources or normal ambient light.