0 inches but it’s fairly lightweight, weighing only 1. 0lb. This particular model does not come as a hard wired detector, the only way to power it remains through the use of batteries and the only smoke/CO detectors from First Alert that can be connected to the home’s power source are the 120V AC Smoke and Carbon Monoxide alarm and the already mentioned OneLink detector. In order to install the First Alert 2 in 1 Z Wave detector, you need to take the mounting bracket and fix it to either the ceiling or the wall using the provided screws don’t mount it in the corners of the room and keep a minimum of 5 feet from any cooking appliances, since the air currents carrying the cooking smoke could get to the smoke sensor, thus triggering unwanted alarms. Afterwards, attach the smoke and CO detector to the mounting bracket by twisting the device into place depending on the spot where you want to install it, you may need to take additional steps to prevent any unauthorized removable – you can lock the battery compartment and/or the detector using the locking pins. As you know, the smoke alarms use two types of sensors to detect any life threatening emergencies: the ionization sensors to detect fast burning fires and the photoelectric sensors to detect fires in their early stages smouldering fires. The ionization sensor uses a chamber filled with ionized air and, when smoke enters it, the sensor triggers the alarm. Because of its nature, the ionization sensor tends to be more sensitive at detecting small particles, therefore more often triggering false alarms. The First Alert 2 in 1 steered clear of the ionization sensor and only went for the photoelectric type. The photoelectric sensor is better suited at detecting larger particles usually from smouldering fires, that don’t erupt immediately into flames by using a light beam inside the detector which doesn’t directly hit the sensor, but will do so in case smoke enters the device and forces the light towards the sensor. Besides the smoke detecting sensor, the First Alert 2 in 1 also has a Carbon Monoxide Electrochemical sensor which has the role of detecting any rising levels of CO inside the room and triggering the alarm when the concentration crosses the safety levels there will be both visual and audible signals – up to 85dB at around 10 feet.