This smoke detector carbon monoxide detector combo is a 2-in-1 carbon monoxide and smoke detector, so you don't need to install them separately Smoke and carbon monoxide detector has a large digital display and is readable. But to save power, the display is not always on. Under normal working state, only the green led light will blink every 60 seconds or so This carbon monoxide and smoke detector features a low battery warning that will alert you to replace the batteries in a timely manner. Sleek design, 360-degree air inlet ensures that smoke or carbon monoxide can enter the detector The installation of smoke detector is easy, we recommend mounting it on a wall or ceiling.If you feel the green led light is too bright, please paste a relatively transparent PVC to reduce the light according to your brightness requirement The sound of combination smoke and carbon monoxide detector is over 85 dB. It is loud enough to be heard. This smoke carbon detector has a test button, you can use it to test its working state Our smoke detector carbon monoxide detector combo adopts photoelectric sensor and electrochemical CO sensor design, dual sensitive sensors to detect smoke or CO independently. This fire alarm smoke detector is powered by 3 batteries, it has a low-battery alarm so that this smoke and carbon monoxide detector will keep its working state. A large LCD display provides you with a clear concentration on both smoke and CO, let you know the real-time smoke or CO level clearly. Once danger happens, this smoke detector will give out sound and LED flash at the same time, providing you a clear indication to leave.