Conventional carbon-monoxide gas detectors detect gas leakage in closed areas like home, garage etc. Gas detectors with electrochemical sensor have stable sensitivity and high performance. Gas detectors have 2 level threshold. When the gas in the ambient reaches 50ppm, the gas detector goes into 1st level alarm. If gas concentration reaches 200ppm, the gas detector goes into 2nd level alarm. When the gas concentration in the ambient reaches below 50 ppm, the gas detector automatically turns back to its normal operating condition.