Three styles. Please pay attention to the choice. Model 1 KR002 Feature: High Sensitivity Dual Sensor DesignCarbon Monoxide fire alarm is a Catalytic Combustion Method Sensor and the Electrochemical Carbon Monoxide Sensor; Protect yourself and your family from two deadly threats. When dangerous concentrations of Carbon Monoxide or Explosive gases are detected, notify you immediately to save your life in the first place. Easy To UsePush/test button - Connect to power 90V-240V or 9V rechargeable battery(not included), The detector will display 3 minutes counting. LCD Digital DisplayThis display clearly shows levels of Gas that the unit has detected and stored-- from 0 to 3000 ppm--and it updates every 9 seconds to indicate any sudden changes. Voice AlarmWhen the concentration of Carbon Monoxide reaches 100PPM or the concentration of Combustible gas reaches 6%, the LCD screen begins to display the concentration value, and the red LED lights flash and emit a loud voice alarm mode -- 85 decibel alarm. Easy Installation & QualityEasy to mount on any wall or ceiling without an electrician;The detector has been rigorously tested and passed UL2034 safety certification, If you have any questions, Please contact us by E-mail, We will give you a SATISFACTORY SOLUTION. Gas Detector Information Plug-in Carbon Monoxide & Explosive Gas Detector is a smart combustible gas combo detector with sound prompt and 9V battery Backup,continuously dispalys of the gas concentration levels from 100PPM-999PPM(50PPM)and will Voice alarm >85 dB when dangerous levels are reached.This detector is a great helper to detect the invisible Gas & CO in the air(such as Natural Gas,Propane,Methane,Liquefied Petroleum Gas,etc)and keep you and your family away from the threat. 9V Rechargeable battery or Regular battery backup for protection even during power outages. Where should install the gas detectors 1.Please confirm the induced gas in heavier than air or lighter than air,the gas is heavier than air:LPG etc. the gas is lighter than air: Natural gas, marsh gas etc. 2.Chooseing the suitable position to install the Detector according to the gas specific gravity.Detecting the gas heavier thanair: Installation height from floor 12-40 in,semi-diameter to gas source