specifications:sensor: electrochemical carbon monoxide sensor detecting range: 0-999ppm sensitivity: 5ppm error: ¡¨¤10% +15ppm the detecting precision is affected by detector itself and the temperature and humidity of the installation environment the best installation environment: 20 numerical readings and note: 3-digit lcd display of levels normal reading: 0 alarm readings: 30 - 999ppm battery capacity display: full, ok, low, dead sensor performance display: malfunction alarm modes: sound, beep, hummer light: red led flashing installation: wall and table power supply range: 110/220/230-240v ac backup battery: 1 x 9v alkaline battery working temperature: 0 - 60¡ãc relative humidity: