Abstract: The present invention is a carbon monoxide or other toxic gas detector. The detector of the present invention detects the presence of carbon monoxide in an air sample by measuring the time required for the sensor circuitry to charge. Such a measurement technique eliminates the inaccuracies inherent in prior art detectors which measure the resistance of the sensor circuitry upon exposure to carbon monoxide. The detector of the present invention is controlled by a microprocessor which enables the detector to retain in memory air sample readings of carbon monoxide or other toxic gas. If the detector registers four consecutive readings which indicate the presence of carbon monoxide in an air sample in a concentration greater than or equal to about 100 ppm, then the alarm of the detector will be triggered, thereby alerting the user to a dangerous concentration of carbon monoxide gas in the air.