A method of indicating the presence of a target gas in a gas volume comprising providing a gas sensing core, configured for detection of the target gas, and a condition sensor within the gas volume, providing a controller, allowing gas to fluidly interact with the gas sensing core, monitoring a target gas measurement output from the gas sensing core, monitoring a parameter output from the condition sensor, recording a parameter output minimum value, calculating a parameter difference, calculating a rate of change of the parameter with respect to time, and indicating the presence of a target gas is detected in the gas volume when the target gas measurement exceeds a target gas measurement threshold value and the parameter difference is less than a parameter difference threshold value.