The first type of sensor is very sensitive to smaller particles, so, they’re very good at detecting fast burning flames, but, unfortunately, are also prone at giving false positives for example, while cooking. The second type of sensors relies on detecting larger particles specific to slow burning, smouldering fires – such as a cigarette left on the sofa by using a light source inside a chamber which points away from the sensor, but will deviate its course towards it at the moment smoke enters this chamber. The First Alert Onelink Safe and Sound uses a photoelectric sensor for detecting smouldering fires and an electrochemical sensor for detecting CO emissions so it uses minimal power to accurately detect any change in the concentration of CO from the atmosphere. In case the sensors detect rising levels of smoke or CO, the LED light will flash a red colour and you’ll hear a voice telling you the location of the detector in case you have more than one devices inter connected. The alerts can be silenced by pushing the Test/Silence button for a minimum of 3 5 seconds or using the app, but be aware that this is only temporary and you will need to identify and fix the problem until the alarm will sound again you get 15 minutes in case the sensor detects smoke and 4 minutes when the sensor detects high levels of CO. The Onelink Safe and Sound smoke/CO alarm can interconnect with other Onelink alarms, so, in case there’s a fire in the kitchen, all the devices will sound the alarm and will tell you the room where the emergency originates.